Cellular Telephony

TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

WIRELESS TERRESTRIAL COMMUNICATIONS: CELLULAR TELEPHONY Ariel Pashtan Aware Networks, Inc., Buffalo Grove, Illinois, USA Keywords: mobile network, mobile terminal, cellular phone, cellular service, cellular operator, mobile subscriber, radio access network, core network, cell site, wireless application protocol, wireless Internet, short message, instant message, emergency call, quality-of-service.

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Contents 1. Introduction 2. Mobile networks 3. Mobile terminals 4. Cellular telephony evolution: from 1G to 3G 5. Cellular services 6. Cellular quality-of-service 7. Billing for cellular services 8. Conclusion Glossary Bibliography Biographical Sketch To cite this chapter Summary

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Cellular telephony encompasses the use of cellular phones to place voice calls, exchange short messages, transmit data, browse the web, and issue multimedia calls. In this topic we describe the evolution of cellular telephony mobile networks, mobile terminal features, and elaborate on the associated cellular services and underlying supporting technologies. 1. Introduction

A wireless mobile communication network enables users equipped with mobile terminals to initiate and receive phone calls. This capability is referred to as cellular telephony. In the following we describe mobile networks and the mobile terminals used by mobile subscribers to carry out cellular calls. We proceed with an account of the history of cellular telephony and elaborate on the evolution of networks and subscriber services, including the convergence of data networks towards the wired Internet standards. Cellular telephony has evolved to include many services that are based on the transmission of data and multimedia, not just voice. Mobile subscriber services offered by cellular operators are described next. The underlying technologies of some services are detailed as well. Finally, we end with a description of cellular telephony quality-of-

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

service and explain how cellular operators bill for user services. 2. Mobile Networks

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Cellular telephony derives its name from the partition of a geographic area into small “cells”. Each cell is covered by a local radio transmitter and receiver just powerful enough to enable connectivity with cellular phones, referred to also as mobile terminals, within its area (Figure 1). The set of cells forms the radio access network, and the radio frequencies used for the transmission of calls and data can be reused between cells. A different type of reuse, digital code reuse, is used in CDMA-based networks described later on. Voice and data exchanged between a mobile terminal and regular phone networks, or the Internet, are transmitted via the mobile network which consists of the cellular operator’s radio access network and core network.

Figure 1: Mobile network

2.1. Cell Sites

A cell site is a site where antennas and radio transmitters and receivers are placed to create a radio coverage area in the mobile network. Cell sites can be omni-sector, meaning that the same frequencies are used in all directions, 3-sector where the site coverage is partitioned into three distinct directional areas, each referred to as a cell (Figure 2), or 6-sector if the partition is into six areas, in which case the site consists of six cells. A separate radio frequency is used for each direction of the communication between mobile terminal and cell site. Communication from the mobile terminal to the cell site is referred to as uplink transmission, and the reverse direction is the downlink.

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

Figure 2: 3-sector cell site

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The spectrum of radio frequencies available for communication is limited and a benefit of a mobile network is its ability to reuse radio frequencies in different cells, provided that radio interference does not affect the calls. This reuse provides for increased network capacity as more mobile subscribers can be supported in a given geographic area. As the number of mobile subscribers increases, more cells can be added or existing cells can be split into smaller ones. Two major factors that impact interference are the distance between cells and the cells’ transmission power. The layout of cells, allocation of frequencies, and transmission power specifications are part of radio frequency (RF) planning carried out by the cellular operators. 2.2. Mobile RF Spectrum

Radio frequencies are allocated to different cellular radio technologies as shown in the map of Figure 3 and associated tables (Error! Reference source not found. - Error! Reference source not found.). Only a few countries are listed as examples of the spectrum allocation.

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

Figure 3: Radio frequencies allocation; (Source: www.ctia.org)

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Country Austria Belgium Finland France Germany Greece Italy Russia

Spain United Kingdom

Cellular Radio Technologies (Frequency - MHz) GSM-900/1800, W-CDMA GSM-900/1800 GSM-900/1800 GSM-900/1800 GSM-900/1800 GSM-900/1800 GSM-900/1800, W-CDMA, TACS-800 GSM-900/1800, CDMA-450/800, TDMA-800, AMPS800, NMT-450 GSM-900/1800, TACS-800 GSM-900/1800 Table 1: ITU region 1 (light blue)

Country Iran Iraq Israel Jordan Kazakhstan Saudi Arabia

Cellular Radio Technologies (Frequency - MHz) GSM-900 GSM-900 GSM-900, CDMA-800, TDMA-800, iDEN-800, AMPS800 GSM-900 GSM-900, CDMA-800, AMPS-800 GSM-900

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

Syria Turkey UAE Uzbekistan

GSM-900/1800 GSM-900/1800, NMT-450 GSM-900, W-CDMA GSM-900/1800, CDMA-800, TDMA-800 Table 2: ITU region 1 (red) Cellular Radio Technologies (Frequency - MHz) GSM-900 GSM-900/1800 GSM-900/1800, CDMA-800, AMPS-800

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Country Algeria Côte d'Ivoire Democratic Republic of Congo (ex-Zaire) Egypt Ethiopia Ghana Kenya Nigeria Senegal South Africa

GSM-900 GSM-900 GSM-900, TACS-800, AMPS-800 GSM-900 GSM-900/1800, TACS-800 GSM-900/1800 GSM-900/1800

Table 3: ITU region 1 (brown)

Country Canada

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Mexico USA

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Country Argentina Brazil

Chile Colombia Costa Rica Ecuador Paraguay Peru Puerto Rico

Cellular Radio Technologies (Frequency - MHz) GSM-1900, CDMA-800/1900,TDMA-800/1900, iDEN800, AMPS-800 GSM-900/1800 GSM-900/1800 Table 4: ITU region 2 (dark blue)

Cellular Radio Technologies (Frequency - MHz) GSM-1900, CDMA 800/1900, TDMA-1900/800, iDEN800, AMPS-800 GSM-1800, CDMA-800, TDMA-800, iDEN-800, AMPS-800 GSM-1900, CDMA-1900, TDMA-800, AMPS-800 GSM-800/1900, CDMA-800, TDMA-800, AMPS-800 GSM-1800, TDMA-800 GSM-800, TDMA-800, AMPS-800 GSM-1900, TDMA-800/1900, AMPS-800 GSM-1900, TDMA-800/1900, AMPS-800 GSM-800/1900, CDMA-1900, TDMA-800/1900, AMPS-800 Table 5: ITU region 2 (green)

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

Cellular Radio Technologies (Frequency - MHz) GSM-900/1800/1900, CDMA-800 GSM-900/1800, CDMA-800, W-CDMA, TDMA-800 GSM-900/1800, CDMA-800 GSM-900/1800, AMPS-800, CDMA-800 CDMA-800, PDC-800, AMPS-800 GSM-900, CDMA-800/1700 GSM-900/1800, TDMA-800, TACS-800, NMT-450 GSM-900 GSM-900, TDMA-800, AMPS-800 GSM-900/1800, AMPS-800, iDEN-800 GSM-900/1800 GSM-900/1800, CDMA-800 GSM-900/1800/1900, CDMA-800, AMPS-800

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Country China China – Hong Kong India Indonesia Japan Korea Malaysia Nepal Pakistan Philippines Singapore Taiwan Thailand

Table 6: ITU region 3 (yellow)

2.3. Subscriber Mobility

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Cellular telephony is different from landline telephony in that the mobile subscriber can place and receive calls while on the move without any disruptions in the calls. When a mobile subscriber travels during a call, the network will maintain the call so that it proceeds uninterrupted by handing it off between cells in the mobile subscriber’s path (Figure 4 ).

Figure 3: Mobile terminal handoff

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

Since adjacent cells use different radio frequencies, the mobile terminal moves from one radio frequency to another in the process of being handed off. The design of a cellular system needs to verify that handoffs are fast so that roaming subscribers don’t experience any noticeable break in their calls.

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To receive a call, a roaming subscriber needs first to be located. To support subscriber location tracking, a cellular network is partitioned into location areas (Figure 5). Each location area consists of a number of adjacent cells and whenever a subscriber moves from one location area to another, a location update indication is sent to the mobile network. The network tracks the current location area for each subscriber so that when there is an incoming call, the network pages all the cells in the current location area. After the mobile terminal responds to the page with an indication of the current serving cell, the call can be routed to the right cell and the mobile terminal alerts the mobile subscriber through ringing that there is a pending call.

Figure 4: Location areas for mobile paging The partition of a cellular network into separate location areas and the corresponding location updates issued by the mobile terminal ensure that subscriber location is an efficient procedure. The alternative, if there are no location areas, is to page the whole network, which could span the whole of a country, whenever there is an incoming call. This would obviously place too high an overhead on a network’s communication channels. The smaller the size of location areas, the higher the number of location updates issued by roaming subscribers. Effective sizing of a network’s location areas

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

ensures that the number of location updates does not negatively impact the network’s communication capacities. 3. Mobile Terminals Today’s mobile terminals provide relatively large color screens. Some have touchsensitive color screens with a stylus used for selections and text input. Besides a radio for cellular telephony, supported local connectivity often includes infrared, USB, and Bluetooth. Many phones include an embedded digital camera, a video player, and some include an MP3 player.

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The internal memory can reach tens of megabytes, and an external memory card is sometimes available too. Java development and run-time environments are often provided so that a large number of applications are made available through the Java development community. Speaker dependent voice commands are enabled in many phones, allowing for hands free operation. Included micro-browsers support a number of markup languages, often including the latest release of the HTML language, HTML 4.01.

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An example cellular phone is shown in Figure 6.

Figure 5: Sony Ericsson P910; (Source: © Sony Ericsson 2006. All right reserved) This particular phone model, the Sony Ericsson P910, has a relatively large screen and a

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

number keypad that can be flipped open to reveal on the back a QWERTY-style keyboard for entering text messages. GSM and UMTS mobile terminals are required to have a subscriber identity module (SIM) card. A SIM is a small form smart card which stores mobile subscriber identifying information, subscription information, preferences, and contacts information. By moving a SIM card from one mobile terminal to another, a mobile subscriber can use this latter terminal and be charged for the calls that are placed on it. The SIM also stores the current location area identity to help the mobile terminal determine if it needs to send a location update message when it is turned on

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4. Cellular Telephony Evolution: from 1G to 3G 4.1. 1G Cellular Systems

The concept of cellular telephony was invented in AT&T’s Bell Labs in the early 1970’s. The first commercial cellular network was the Nordic mobile telephone (NMT) network deployed in the Scandinavian countries in 1981. The advanced mobile phone service (AMPS) cellular system was deployed in the United States in 1983 and was followed by other analog deployments across the world. The total access communications system (TACS) is another analog system developed by Motorola in the early 1980s. These first analog-technology mobile systems are referred to as first generation or 1G.

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The analog systems use a frequency division multiple access (FDMA) radio system where each user channel has a dedicated carrier band. For example, the AMPS system uses a 30 KHz wide carrier band for each mobile user channel. An improvement upon the AMPS system is Narrow AMPS (NAMPS) where each carrier band is only 10 KHz wide so that three times as many mobile subscribers can be supported. An add-on to the AMPS system is cellular digital packet data (CDPD) developed in the early 1990s and first deployed in 1994. CDPD enabled the transfer of packet data over analog channels by leveraging idle channels for short data transmissions. Data speeds reached up to 19.2 Kbps. 4.2. 2G Cellular Systems

As the number of cellular subscribers grew and there was a need for increased network capacity, digital systems were invented. These included, among others, the European initiated global system for mobile communication (GSM) and the United States initiated code division multiple access (CDMA). The 2G version of CDMA is referred to as cdmaOne. These digital systems form the second generation or 2G. GSM was developed by the European Telecommunications Standard Institute (ETSI) in the late 1980’s, and the IS-95 CDMA standard, known as cdmaOne, was introduced by the TR45.5 subcommittee of the Telecommunications Industry Association (TIA) in 1993. Other 2G systems, of smaller scale, included the Japanese personal digital cellular (PDC) and the TIA time division multiple access (TDMA) IS-136 used mainly in the Americas.

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The GSM system is a TDMA radio system with carrier bands that are 200 KHz wide. Each band is comprised of eight bearer slots. This is a circuit switched system where a dedicated bearer slot (a circuit) is allocated to each voice communication so that up to eight mobile subscribers can be supported on one carrier band. A single cell will typically support multiple carrier bands. In GSM, the radio frequencies used for the carrier bands can be reused between cells as long as the radio transmitters that use the same frequencies are not in adjacent cells. The reuse pattern is referred to as a “frequency plan” and is engineered so as to minimize radio interference.

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Another TDMA system, introduced by Motorola in 1994, is the integrated digital enhanced network (iDEN), a digital wireless standard designed to work in special frequencies originally designated for analog Specialized Mobile Radio (SMR) networks used for dispatch operations. iDEN provided a unique capability as its cell phones include an integrated push-to-talk (PTT) capability, similar to walkie-talkie that works across a wide area network, on the same cell sites used for cellular telephony. cdmaOne uses a different radio technology referred to as “spread spectrum” where the radio spectrum is divided into carriers which are approximately 1.23 MHz wide. In cdmaOne, each voice channel is assigned a unique code within the carrier and the voice signal is spread to a transmitted rate of about 1.23 Megabits per second. Since all user calls in a given cell share the same channel band, the only way to distinguish between the calls is through the unique code assigned to each voice channel. The unique code is used to spread the original signal and then to decode the signal at the receiver end. The cdmaOne network utilizes universal frequency reuse where the same frequency can be reused in every cell since what distinguishes the voice channels are the unique codes. This enables greater network capacity as compared to the TDMA-based systems. 4.3. 2.5G Cellular Systems

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The 2G systems support basic data services with limited capacity since a single voice channel is used for the data transmission. Only one wireless bearer slot of a GSM carrier band is allocated to the data transfer so that the transfer rate is limited to 9.6 kbps. Furthermore, the mobile subscriber is charged, as for voice calls, on a connection-time basis. An improvement to this scheme was made available in the form of high-speed circuit switched data (HSCSD) where multiple bearer slots are made available to the same call. The downside of this scheme is that the additional bearer slots are no longer available to other voice calls for the duration of the data call. To provide better support for data services, ETSI developed the general packet radio service (GPRS), a packet transmission system that overlays GSM and inter-works with external packet data networks such as the Internet. GPRS is a 2.5 generation, or 2.5G, wireless communication system. In a GPRS system, each mobile terminal is assigned an IP address. The assignment can be static, as determined by the cellular operator, or else dynamic, on a per connection basis. When the mobile terminal is on, it is always connected to GPRS. The mobile subscriber is charged for the amount of data transferred, not on a time basis as done for voice calls. A GPRS-enabled mobile terminal can use between one and eight wireless

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bearer slots of a GSM carrier band. The bearer slots are dynamically allocated to a user when there are packets to be sent; the higher the number of assigned slots, the faster the data transfer with speeds of up to 115 kbps.

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An operator’s mobile network is also referred to as a public land mobile network (PLMN). Figure

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Figure 6 shows a GSM PLMN with an overlaid GPRS network; the element and interface names are as specified by the ETSI standards. The GSM network elements used for handling cellular telephony calls are the BSS, MSC/VLR, and HLR.

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Figure 6: GSM circuit & GPRS packet networks

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

The BSS is the base station subsystem that includes the BTS and BSC. The BTS is the base transceiver station that includes the antennas and handles the radio transmission to the mobile terminals. The BSC is the base station controller which manages several BTSs. The BSC transmits voice calls to the MSC and contains the packet control unit (PCU) for handling data traffic to the GPRS network. The MSC is the mobile switching center; it switches voice calls between the mobile terminals and the public switch telephone network (PSTN). It handles the setup of calls and allocation of circuits between mobile terminals and the PSTN, or between mobile terminals. The VLR is the visitor location register, often co-located with the MSC. This database stores temporary information about the mobile terminals in its area. The HLR is the home location register. This database contains the mobile subscribers profile information that includes the list of subscribed services. The HLR authenticates mobile terminals that want to access the mobile network and also records the mobile terminal locations in the network.

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The GPRS network includes two new nodes, the serving GPRS support node (SGSN) and the gateway GPRS support node (GGSN). The traffic from the mobile terminal is split at the BSC with voice sent to the MSC and data packets sent to the SGSN. The SGSN is responsible for tracking the GPRS mobile terminals in its area and for routing data packets to the mobile terminals. It keeps a record of the BSC to which each mobile in its area is assigned. The GGSN serves as a router that interfaces between the Internet, or other packet data network, and the IP-based GPRS network. The GGSN allocates IP addresses to the mobile terminals when these are allocated dynamically, and routes mobile-destined packets to the appropriate SGSN. 4.4. 3G Cellular systems

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The evolution towards third generation cellular systems (3G) was driven by the need of higher capacity, faster data rates, and better quality-of-service (QoS). Also prominent was the desire to define a new system that resolved many incompatibilities between the different standards, mainly GSM and cdmaOne, so as to facilitate, for example, mobile roaming between the different systems. This work was spearheaded by the International Telecommunications Union (ITU) and referred to as International Mobile Telecommunications 2000 (IMT-2000). The IMT-2000 effort could not reach agreement on one common standard and now consists of a family of standards to handle the evolution of GSM and cdmaOne.

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Some of the standards are based on wideband CDMA (W-CDMA), also referred to as universal mobile telecommunications systems (UMTS); these are worked on by the original GSM proponents and handled by the Third Generation Partnership Project (3GPP) established in 1998. The stated objectives of 3GPP are to develop a 3G mobile system based on evolved GSM core networks and the radio access technologies that they support. In addition, 3GPP handles the development of GSM and enhanced data rates for GSM evolution (EDGE) standards. 3GPP reported in April 2006 that some 55 million subscribers worldwide were supported by 105 W-CDMA commercial networks.

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The evolution of the cdmaOne standard, referred to as cdma2000, is managed by another standards body, 3GPP2, established in 1999. 3GPP2 is a collaborative 3G telecommunications specifications project that comprises North American and Asian interests developing global specifications for ANSI/TIA/EIA-41 cellular networks. Another organization that is actively involved in the progression of CDMA networks is the CDMA Development Group (CDG), an international consortium of companies who have joined together to lead the adoption and evolution of CDMA wireless systems around the world. As of March 2006, the 3GPP2 organization reported that there were over 147 cdma2000 commercial networks serving more than 225 million mobile subscribers worldwide. The data rates for transferring data between the mobile terminals and the network increase with each new cellular generation. The 3G systems are expected to deliver bit rates in the hundreds of kbps, and up to 2 Mbps in stationary/nomadic user environments. UMTS employs a 5 MHz channel carrier width to deliver these higher data rates and increased capacity, a much wider carrier compared to the 1.23 MHz wide carrier of 2G networks. In addition, unlike the previous generations, one of the new

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

features included in the design of 3G networks is the assurance of quality-of-service. Mobile subscribers that pay for a data service expect the cellular operator to deliver data at a rate not below a pre-agreed upon lower limit. 4.4.1. EDGE

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While enhanced data rates for GSM evolution (EDGE) do not meet all the objectives of a 3G system, EDGE offers significant higher data rates compared to GPRS. EDGE uses an enhanced radio modulation scheme which allows sending many more bits of information in each GSM bearer slot. The new modulation scheme requires more sophisticated transmitters and receivers in the mobile terminal and the network BTS. EDGE supports nine different coding schemes with bit rates ranging from 8.4 to 59.2 kbps. The higher bit rates are used when there is very little radio interference in the mobile terminal to network transmissions. EDGE is considered an interim step, or complementary technology, in the migration to the W-CDMA systems. 4.4.2. W-CDMA

The W-CDMA system uses wideband direct-sequence CDMA (DS-CDMA) technology in a 5 MHz bandwidth to support the IMT-2000 data rate requirements of 384 kbps wide-area coverage and 2 Mbps local coverage. In the UMTS network, the BSS is renamed the radio network system (RNS), and the BTS is called Node B. The BSC functionality is replaced in UMTS by the radio network controller (RNC). As in the 2.5G network, the RNC routes voice to the MSC and data packets to the SGSN. UMTS defines new interfaces: Uu: mobile terminal to Node B; this is the W-CDMA air interface. Iub: Node B to RNC. Iu: RNC to the core network (comprises the IuCS, IuPS, and Iur). IuCS: RNC to MSC circuit switch interface. IuPS: RNC to SGSN packet switch interface. Iur: RNC to RNC (this is a new interface type, not defined in 2.5G).

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

Figure 7Figure 8 shows the UMTS radio elements and their interfaces to the core network. The core network includes the same elements of the 2.5G network, and supports circuit services via the MSC and packet services via the SGSN and GGSN. UMTS defines new interfaces:

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Uu: mobile terminal to Node B; this is the W-CDMA air interface. Iub: Node B to RNC. Iu: RNC to the core network (comprises the IuCS, IuPS, and Iur). IuCS: RNC to MSC circuit switch interface. IuPS: RNC to SGSN packet switch interface. Iur: RNC to RNC (this is a new interface type, not defined in 2.5G).

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

Figure 7: UMTS network for circuit and packet services The Iur interface was defined so that all radio resource management functions are performed in the RNS without any support from the core network. For example, mobile terminal admission control, mobile terminal handover, including serving RNC

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relocation when the mobile terminal roams to an area served by a different RNC, are handled exclusively by the RNCs. The terrestrial interfaces, Iub, Iu, and Iur use the asynchronous transfer mode (ATM) protocol for data exchange between the connected elements. The 3G RNC enhances the operations performed in the 2G BSC. For example, the RNC prioritizes the mobile terminal connections according to QoS levels of agreement between the mobile subscriber and cellular operator. In addition, the 3G mobile terminal can simultaneously receive data from multiple cells and combine them into a better signal.

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A key aspect of 3G is the support for different levels of service as defined by 3GPP’s QoS classes, also referred to as traffic classes. These classes include: conversational class (e.g., voice applications) streaming class (e.g., video applications) interactive class (e.g., web browsing) background class (e.g., file transfer)

Additional detail on QoS is provided in the ‘Cellular quality-of-service’ section. 4.4.3. cdma2000

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The cdmaOne air interface has evolved in a few phases. The cdma2000 1X system offers higher bit rates, compared to cdmaOne, of approximately 144 Kbps. The next version, cdma2000 1XEV-DO (evolution data optimized) allocates a separate 1.25MHz wireless carrier for data so that data rates can reach up to 2.4Mbps. A follow-on version, cdma2000 1XEV-DV (evolution data and voice) recombines voice and data into a single wireless carrier with QoS support for real-time data exchanges.

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The cdma2000 core network and defined interfaces (Figure 9) has also enhanced the cdmaOne network to handle data and includes a separate data network, similarly to the separate GPRS network in GSM. This data network, the packet core network (PCN), includes a new network element, the packet data serving node (PDSN), an enhanced BSC which routes voice calls to the MSC and data packets to the PDSN. Another new element is the authentication, authorization, and accounting (AAA) server used in IP session establishment. The PDSN routes data packets between the radio access network (RAN) and the Internet and supports the IETF Mobile IP protocol. Mobile IP enables mobile terminal mobility so that a terminal that attaches to a visited network PDSN can send and receive packets addressed to its home IP address.

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

Figure 8: cdma2000 network for circuit and packet services

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Cellular telephony has evolved from being just a voice service to providing a rich collection of data and multimedia services. To enable these new services, radio access and core network standards are being defined by the 3GPP and 3GPP2 organizations, while the open mobile alliance (OMA) standards organization delivers technical specifications for application and service frameworks. Key cellular services and the associated supporting technologies are described in the following.

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5.1. Text Messaging

Text Messaging is the ability to send and receive short messages on a mobile terminal. These messages are also referred to as Short Message Service (SMS) messages since the length of a message is limited, for example, to 160 characters. Longer messages may usually be sent too however, they are sent in parts of 160 characters (if this is the limit), and the mobile subscriber is billed separately for each part. A mobile subscriber is made aware of a received text message on his mobile terminal through a beep and an icon (for example, an envelope) displayed on the terminal’s screen. If a mobile terminal receiver is turned off, or the mobile subscriber is on a call, text messages are stored in the network and delivery is retried until successful for up to a limited number of hours (for example, 72 hours). How does a mobile subscriber enter text on his terminal? There are two entry types for mobile terminals that do not have a small keyboard. These are the “multitap” and the predictive text entries. In the “multitap” case, the user has to press a single key multiple

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

times to select the desired character. With predictive text entry, a built-in dictionary tries to predict the typed word, based on the sequence of user keystrokes. High-end mobile terminals are equipped with small keyboards with a QWERTY key layout similar to the one on regular keyboards. Text messages can be sent to any wireless phone number. The user types in the receiver’s mobile terminal number and the message will be delivered across mobile operators and also internationally. Typical billing for SMS is on a per message basis with more economical packages available for a monthly fee. For example, in the USA, the typical cost of an SMS message is $0.10. Higher rates are charged for international messaging.

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Group text messaging is a feature that allows a mobile subscriber to send a text message to a wireless phone number that represents a group of users. Each group member is identified by his phone number so that a send operation translates to a number of text messages, one per group member. SMS core network

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SMS messaging is asynchronous with no correlation of a mobile subscriber reply to a previously received message. SMS messages are sent to and received from an SMS Service Center (SC) over the Short Message Transport Protocol (SMTP) – see

Figure 9Figure 10. The SMS SC is connected to the cellular operator’s network through an SMS Gateway / Interworking MSC. For mobile-originated SMS, the mobile terminal establishes a signaling connection with the mobile switch center (MSC), and the SMS is transferred over this control channel to the MSC. The MSC then transfers the SMS, via the SMS Interworking MSC to the SMS SC.

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The SMS SC is responsible for delivering received SMS messages. The SMS SC conveys the message to an SMS Gateway MSC that in turn, interrogates a relevant HLR for the destination MSC where the mobile subscriber is available. ITU Signaling System number 7 (SS7) is used to transport the SMS message to the MSC. The MSC then sets, if need be, a signaling connection to the destination mobile subscriber’s terminal for SMS delivery.

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If the SMS message cannot be delivered, for example, if the destination mobile subscriber terminal is off, then the SMS SC will hold the message up to a pre-set time limit (for example, 72 hours) before discarding it. When a mobile subscriber’s terminal reconnects to the cellular network, the HLR will send a corresponding notification to the SMS SCs that have indicated an available message for the mobile subscriber. This allows the notified SMS SCs to retry the sending of an SMS. If the transport network is GPRS, then the MSC /VLR SMS delivery function is handled by the Serving GPRS Support Node (SGSN), and the delivery of SMS messages occurs between the SGSN and the mobile terminal. For networks where the transport is all IPbased, the MSC /VLR SMS delivery function is handled by the IP Short Message Gateway (IP SM Gateway). The 3GPP organization has authored corresponding specifications that enable the delivery of SMS over an IP access to the cellular network.

Figure 9: SMS core network 5.2. Instant Messaging Instant messages (IM) are short text messages exchanged between users that want to chat in real-time. After a user signs on to IM from a mobile device, a list of friends (referred to as a buddy list) appears on the mobile subscriber’s screen using familiar screen names or IDs. The mobile subscriber can send a message to the IM service

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

requesting to see, with the help of special icons, who is online and available to chat, busy, or offline. IM messages can be sent only to users that are online. Each user is identified by a text identifier referred to as “short code” or “screen name”, and messages are sent to these identifiers, not to phone numbers as in SMS.

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Most mobile IM systems were designed as extensions of wired Internet services. For example, AOL Instant Messenger (AIM) and Yahoo! Messenger offer mobile services that extend the reach of IM to mobile users. In the case of AIM, when mobile subscribers first sign on, the most current 25 buddies from their respective PC buddy list are copied into their mobile buddy list. When users sign on to IM from their mobile device, a mobile icon will typically appear next to their screen name in their friends' buddy list window to let them know they are using a wireless device. There are often two ways to access the IM service. The mobile subscriber can download an IM application to the mobile terminal. Alternatively, some IM services provide mobile users with a browser interface. AOL, AIM, and Buddy List are registered trademarks of America Online, Inc. Instant Messenger is a trademark of America Online, Inc. 5.3. Multimedia Messaging

Multimedia Messaging (MMS) allows sending pictures, video, and voice messages to another mobile terminal or e-mail address. Mobile subscribers can take a photo or video using their mobile terminal's embedded camera or a camera attachment, and send it to a wireless number or e-mail address. Similarly, they can record a voice message on their mobile terminal and send it as a MMS message.

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Multimedia messages can also be received on the mobile terminal as an email message that is sent to an e-mail address that includes the recipient’s phone number. Typically, a mobile subscriber will first receive a text message and then, depending on the message content, can decide if he wishes to download the multimedia message. Multimedia messages sent to non-multimedia capable mobile terminals are typically delivered as text messages. The text message could include a link to an Internet address where the message can be viewed online. 5.4. E-mail

Mobile e-mail allows users to check wireline e-mail on their mobile terminal. Services that allow mobile access to e-mail include Yahoo!, Microsoft’s Hotmail, and AOL’s mail. The mobile subscriber would typically download on the mobile terminal a dedicated application that can connect to the mobile subscriber’s mail inbox. To check for e-mail, a mobile subscriber would open the mail application, sign in to the e-mail server, and then is presented with his inbox e-mails. The mobile subscriber can scroll through the e-mail headings and select those that he wishes to download to his mobile terminal. Some e-mail services provide “e-mail alerts” that are sent to a mobile subscriber’s mobile terminal to inform the mobile subscriber that there are new e-mails in his inbox. Newer mobile terminals allow viewing e-mail attachments.

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

5.5. Emergency Calls In the US and Europe, government mandates required cellular operators to provide the location of subscribers that dial emergency calls (911 in the US and 112 in Europe). For example, the US Federal Communications Commission (FCC) passed a mandate in 1999 that requires operators to find 95 percent of subscribers within 150 meters for handset-based location technology and within 300 meters for network-based location technology.

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In addition, the cellular operators are required to route emergency calls to the correct emergency call center. Since there was no similar accuracy mandate in Europe, European cellular operators typically use the serving cell’s identifier to derive the subscriber’s location. In this case, the location accuracy varies with the cell size. Network-based location technologies use location measurement units (LMUs) installed at the cell sites. The LMUs listen to signals emitted by the mobile terminals and measure signal propagation time from the terminals. Measurements are forwarded to a central site, the location service center, which uses a triangulation method, referred to as uplink time difference of arrival (U-TDOA), to compute mobile terminal locations.

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Handset-based location technologies are often based on global positioning system (GPS) receivers embedded in the mobile terminal. These receivers process signals sent from the US government satellite navigation system that comprises 24 satellites that orbit the earth. At least five satellites are visible from any point on earth and the receiver requires four satellites to compute its position in three dimensions using a triangulation technique. The European Space Agency is building a system similar to GPS, referred to as Galileo, which includes 27 satellites and will be operational in 2008.

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5.6. Wireless Internet

Access to the wireless Internet is provided through a micro-browser on the mobile terminal. The types of content that can be accessed include: • Sports: to receive the latest scores from sport news channels. • News & Finance: to read articles from channels such as CNN and major newspapers. • Entertainment: to receive movie times and reviews, dining recommendations, etc. • Weather & Travel: to check the forecast from a weather channel, to get flight times and traffic reports, etc. Location-based services form a special category of Internet content services that are of primary interest to mobile subscribers. These services are designed to provide information that is relevant to the subscriber’s locale. In some services the subscriber types in the location, for example, a postal code, and specifies a maximum distance that bounds the area of interest for the requested information. Some restaurant finders use

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

this approach. In other instances, the cellular operator tracks the subscriber’s location or the mobile terminal can provide this information if it includes a GPS receiver. Navigation services, for example, can leverage location information to guide the subscriber to a specified destination using visual and audible turn-by-turn driving directions. People and vehicle tracking services also use location data. They allow subscribers to receive on their mobile terminals real-time location information on the whereabouts of co-workers or of vehicles of a fleet. Similarly, safety concerns may prompt subscribers to track the location of their family members.

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In addition to the above described mobile services, the mobile subscriber can access any web site by entering its URL Internet address. In some cases the web sites can adapt their content to the terminal’s micro-browser. Alternatively, some micro-browsers can adapt the content of web sites on the terminal device. For example, the Opera microbrowser includes Small-Screen Rendering™ technology. With this technology, the page is reformatted to fit inside the mobile terminal’s screen width so that there is no need for horizontal scrolling.

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Micro-browsers & wireless Internet architecture Access to wireless Internet web sites is done with the help of micro-browsers that execute on the mobile terminals. Like their desktop counterparts, micro-browsers render markup files on the device screens. Markup languages include the latest versions of HTML and XHTML (an XML version of HTML). The first versions of micro-browsers were released in the late 1990’s and supported special markup languages such as the handheld device markup language (HDML) developed by Unwired Planet (now Openwave Systems), and the wireless markup language (WML) specified by the WAP Forum (now the Open Mobile Alliance, OMA). WML introduced the concepts of cards and decks. A card is a basic unit of interaction and corresponds to a mobile terminal screen. The deck is a collection of related cards sent to the mobile terminal as a package to improve the subscriber interaction experience through fast access to locally stored screens. In Japan, Access used a different approach by adopting a subset of HTML, compact HTML (cHTML) for its micro-browsers as it wanted to provide mobile content authors with a language they are familiar with from the wired Internet. The W3C standards organization, which authors HTML specifications, produced in 2000 the XHTML Basic markup, a subset of XHTML that is suitable for mobile terminals. The WAP Forum (now OMA) extended XHTML Basic and produced the XHTML mobile profile (XHTML MP). In 2001, the WAP Forum specified WML 2.0; it consists of two markup languages: XHTML MP and WML 1.3, the latter for backward compatibility purposes. The WAP Forum specified an architecture and wireless-optimized protocol, the WAP protocol, to support wireless Internet access (Figure 11). The WAP protocol is multilayer starting at the Transport layer through the Application layer and is used between a mobile terminal and a WAP gateway. The WAP gateway performs protocol conversions between the wired Internet protocols and the WAP protocol. Additional functions performed by the gateway include data compression for transmission over the air,

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

terminal access checking, security, domain name resolution, and data caching.

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A unique capability of the WAP architecture is the ability to push unsolicited content to a mobile terminal. This capability could be used by location-based services that wish to alert subscribers of local event happenings. To enable the push capability, the WAP forum specified a push architecture that includes a push initiator (PI) on the network server side, and a push proxy gateway (PPG) that uses a Push Over-the-Air protocol.

Figure 10: WAP 2.0 network for wireless Internet

The WAP Forum specified in 2001 the WAP 2.0 specification that represents convergence to the Internet standards. The over-the-air protocols include the regular HTTP and TCP protocols that render unnecessary the protocol conversions in the WAP gateway. Data compressions can still take place in the gateway for improved wireless link utilization. With the availability of HTTP, the WAP 2.0 push capability is implemented using standard HTTP POST requests from the PPG to the mobile terminal. 5.7. Video Service and Mobile TV

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Video-on-demand is a service available in 3G networks. It allows mobile subscribers to get TV clips from their favorite programs, music videos, breaking news stories, weather information, and sports clips. Video clips typically have a length of a few tens of seconds. Among the early providers is the Japanese NTT DoCoMo operator; they provide an I-motion video service on their 3G network since 2001. Mobile TV is a relatively recent live broadcasting service that is also offered in 3G networks. Vodaphone is among the cellular operators offering this service. Mobile users can subscribe to live broadcasting packages from TV networks such as Sky News, Sky Sports News, and CNN. 5.8. Push-to-talk

A walkie-talkie type of communication that allows mobile subscribers to communicate at the push of a button is offered by the Nextel (now Sprint) cellular operator. This service is referred to as push-to-talk (PTT). Subscribers can communicate either on an individual basis or to a group of subscribers, as long as all group members are signed on to the same PTT service. This latter group call is similar to a conference call with the added advantage of an easy call setup by simple selection of a group name in the

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

subscriber’s contacts list. The Nextel PTT service is supported by Motorola’s iDEN network which provides fast call setups that are typically under one second. Initially, this service was offered in major metropolitan areas and it is now offered on a country-wide basis, where available, and even across selected countries. For example, by pushing a single button a PTT call can be established between the US and Argentina.

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Unlike regular cellular calls which are billed according to the number of minutes used, PTT calls are usually tracked and billed per the number of seconds used. Other cellular operators have deployed similar PTT services implemented in software on top of existing cellular networks. In these software-based services, referred to as push-to-talk over cellular (PoC), call setup times are typically longer than those on the special purpose iDEN network. 5.9. IP-based Multimedia Communication

Motivated by the desire to leverage Internet applications, services and protocols, the 3GPP organization took on the work initiated by the 3G.IP organization to define an IP Multimedia Subsystem (IMS). IMS enables cellular operators to offer their subscribers multimedia services based on the Internet. IMS provides peer-to-peer communication for IP-based services such as voice-over-IP (VoIP), push-to-talk over cellular (PoC), multiparty gaming, videoconferencing, messaging, presence information and content sharing. IMS network architecture

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The IMS network architecture (Figure

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Figure 11) is a core network architecture that leverages the IETF session initiation protocol (SIP) for session management and service control. In SIP, a destination address is a special uniform resource identifier (URI) called a SIP URI, similar in form to an email address. For the underlying IMS networking protocol, 3GPP has selected IPv6,

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whereas 3GPP2, which has adopted the same IMS architecture, allows both IPv4 and IPv6. The architecture elements include the proxy call service control function (P-CSCF), the interrogating CSCF (I-CSCF), and the serving CSCF (S-CSCF). The 3GPP defined home subscriber services (HSS) element contains subscriber information needed to establish calls and IMS sessions. It extends the information in the HLR and provides support for user security, authorization, mobility management, identification and service provisioning for both circuit switch, packet switch, and IMS services.

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All communication with mobile terminals is handled by the P-CSCF through existing radio access networks such as the UMTS RNS. The I-CSCF roles include assigning a S-CSCF to a mobile subscriber performing SIP registration. The assigned S-CSCF

shown in

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Figure 11 is the subscriber’s home network S-CSCF.

The S-CSCF implements the SIP registrar functionality and session control. Mobile terminal registration requests are handled by the S-CSCF; this element retrieves subscriber profiles from the HSS, handles session requests, and provides notifications to communicating endpoints.

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

Figure 11: IMS network for packet services The S-CSCF also provides an IMS service control (ISC) interface to external SIP application servers that provide IP services to mobile subscribers. The SIP application servers can provide terminating or originating SIP-based services. After a mobile is registered it can setup or receive SIP calls. During call setup, the communicating terminals (mobile or fixed) exchange information on the media components of the call (voice, video, etc.) and the corresponding quality-of-service so that the call can meet user functionality and quality requirements. 6. Cellular Quality-of-service

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6.1. Basic QoS Concepts

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Cellular services, as described in the previous chapter, connect a mobile terminal with a network element (could be another mobile terminal) in what is referred to as an end-toend network connection. With each cellular service could be associated a quality-ofservice (QoS). QoS can be either measured or else depends on user-based subjective assessments. There are three major aspects to QoS: 1. Network access

Network access is the ability to connect to a cellular system. When a user hears a busy signal on the mobile terminal, this is an indication that the call is blocked since the surrounding cell sites are busy servicing other subscribers. Also, the lack of cellular coverage in a given area affects the ability of subscribers to place or receive calls, or transmit data, in that area. 2. Maintaining a connection The mobile terminal needs to stay connected to the network after a call was setup or a data transmission was started until the user hangs up. The network can drop cellular

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calls or interrupt data transmissions. Dropped calls and interrupted data transmissions can occur due to radio interference, failed handovers between cells, or when the subscriber moves to an area with no cellular coverage. 3. Speech and data transmission quality The technical capabilities of a mobile terminal and of the cellular network elements can affect the quality of speech and data transmission. Environment factors such as radio interference can also impact the quality of a connection.

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Monitoring of QoS can take place via network statistics, operator drive tests, and subscriber calls into customer support. Network statistics are the most useful means to track QoS, and have the advantage that they are collected automatically. Processing of the statistics can also provide valuable information to network engineers for specifying cell traffic-load sharing or for planning network growth as they can indicate usage trends. Operator drive tests, in contrast, are labor intensive and provide QoS indicators for mobile traffic at ground level only. However, they can help pinpoint the root cause of problems in the network. Finally, subscriber calls provide an immediate indication of an existing issue. Further analysis is needed to determine what is causing the problem reported by the caller.

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The statistics collected in a mobile network include, among others, the dropped call rate, the average time between dropped calls, the blocked call rate (provides an indication of congestion), the call completion success rate, and the handover success rate. Network elements collect the statistics and upload them every fixed time interval (for example, 15 minutes) to a statistics processing site. Busy hour statistics provide an indication of a network’s operation during peak traffic (there is one busy hour in a day). Statistics can be processed on a network element basis (for example, a cell or a BSC), on a networkregion basis, or on a network-wide basis.

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6.2. UMTS QoS Architecture

To realize a QoS for any cellular service, underlying bearer services (i.e., transport services) have to provide QoS provisioning and management functionalities. Each bearer service provides QoS functionality for service control (for example, network resource allocation), for signaling (for example, call priority), and for user data transport (for example, the marking of data units for specific quality requirements). Figure 13 provides a simplified view of the UMTS QoS architecture as defined in 3GPP. The service QoS is realized by the QoS functions provided in the underlying mobile terminal local bearer service, the UMTS bearer service, and the external bearer service. The mobile terminal local bearer service could consist, for example, of a QoS-enhanced socket API. The UMTS cellular operator is responsible for the UMTS bearer service and can establish service level agreements (SLAs) with the operators of external bearer services to enable an end-to-end QoS level.

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

Figure 12: Simplified UMTS QoS architecture

The UMTS bearer relies on the QoS mechanisms provided by the supporting radio access bearer service and the core network bearer service. The radio access bearer service transports signaling and user data between the mobile terminal and the core network edge. The core network bearer service provides the backbone that connects the core network edge with a core network gateway (GGSN) that interfaces to external networks. The UMTS packet core network enables different backbone bearer services for a variety of QoS needs. UMTS supports different levels of service as defined by 3GPP’s QoS classes, also referred to as traffic classes. These classes include:

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conversational class streaming class interactive class background class

The conversational class is targeted at real-time exchanges between humans such as voice, voice-over-IP, and video telephony. These exchanges are very delay sensitive. The streaming class is also delay sensitive, although to a lesser degree. Typical applications are video and audio streaming. The interactive class is for the exchange of information between a mobile subscriber and the network as for example in web browsing, chat applications, and e-mail. Finally, the background class is mainly for mobile terminal to network information exchange such as file and application downloads. Therefore, traffic in the background class has a lower priority than the interactive class. Since the last two traffic classes are less delay sensitive, they typically provide better error handling by means of packet retransmissions which cannot take place in real-time exchanges.

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

In GPRS, each packet data session between a mobile terminal and a gateway element (GGSN) is associated with a Packet Data Protocol (PDP) context. The PDP context includes a QoS profile that specifies QoS attributes such as delay, service precedence, reliability, mean throughput, and peak throughput. All application flows share the same PDP context. In UMTS, the PDP context mechanism is improved to optimize the traffic flows of multiple applications. Different applications may require separate UMTSdefined QoS classes, and a distinct PDP context can be associated with each connected application on the mobile terminal. 7. Billing for Cellular Services

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7.1. Voice and Data Billing

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Cellular operators use billing procedures to charge mobile subscribers for services such as voice and data. Billing consists of collecting network-generated call detail records (CDRs) that indicate resource usage. CDRs are typically generated in the mobile switch (MSC) and then transmitted in batch files to a billing center for further processing. In the first generation cellular systems, 1G and 2G, users are charged based on connection minutes for both voice and data. With the advent of 2.5G cellular systems, billing systems needed to cope with different ways to collect billing information and charge the mobile subscriber. Cellular operators deployed Internet protocol (IP) billing models where resource usage is collected from additional servers, routers, and gateways. The new data services such as e-mail, SMS, and web browsing did not fit any more the time-base billing model. In the case of web browsing, for example, the subscriber is always on-line. The same applies for e-mail, where the mobile subscriber may get during the day notifications about new e-mails and request to download these to the mobile terminal. To cater for these services, new billing models emerged where the charge is based on the amount of data transferred. Alternatively, a mobile subscriber can sign on to flat-rate billing. In this case, the subscriber is charged a fixed monthly fee for data transfers.

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7.2. Content-based Billing

An additional billing model takes into consideration the type of data transferred. This is a content-based billing approach and is used, for example, for SMS, instant messages, and multimedia messages. For each of these message types the cellular operator can charge a data-type dependent rate.

Operators cannot be expected to provide their subscribers with all the content they require. In an open access model, subscribers can access any web site and retrieve its content. Some sites charge a monthly fee for their content so that subscribers need to pay the content provider for content access and the cellular operator for data transfer. A successful billing model was put into place in the i-mode service provided by Japan’s NTT DoCoMo. DoCoMo enables mobile subscribers to access the Internet via its imode service launched in1999. For each content site that requires a monthly fee, DoCoMo bills the subscriber on behalf of the content provider and takes a 9% share of the bill for its billing service. In addition, mobile subscribers are billed for the data

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transfers. In this billing model, content providers are relieved of the customer billing chores and the mobile subscribers see just one integrated bill that covers both content access and data transfer. Some operators offer content packages that group a number of content providers under one monthly fee. For example, for a fixed monthly fee, Cingular Wireless video service allows unlimited access to news videos of content providers such as CNN, Fox News, the ESPN sports channel, The Weather Channel, and others. Other premium video channels, for example, Music Choice, and Home Box Office (HBO) are available for an additional monthly fee.

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A new service that may impact billing is the capability of cellular operators to track the location of mobile subscribers. With the inclusion of new mobile tracking capabilities such as GPS receivers in the mobile terminals and the operator’s collection of subscriber location records, operators could charge separately for location information. This latter information could be used by location-based services such as yellow pages and travel guides. For each type of content, a user may want a specific quality guarantee of the data transmission. One of the touted advantages of 3G systems is their ability to provide different levels of quality-of-service. Mobile subscribers pick a desired level of service and pay accordingly a different rate. The cellular operator needs to record a subscriber’s selected quality-of-service level and charge the appropriate rate. 8. Conclusion

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Cellular telephony has undergone tremendous development and change since the first cellular system deployments in the early 1980’s. From a voice centric system that enables users to place phone calls over the air, cellular telephony has evolved to support many data services that include information retrieval, message exchange, web browsing, multimedia calls, and even live TV programs display. We reviewed in this topic the history of cellular technology, the major mobile network architectures and associated technologies, the operator provided services, as well as quality-of-service and billing procedures. In recent years, cellular operators have put a major emphasis on the introduction of new and appealing data-based services. These have transformed the phone-like mobile terminal to a messaging and information retrieval device. Mobile subscribers can now be reached and informed in a variety of ways, not just via phone calls. This combined ability of voice, message, and information connectivity has interesting work and social implications. Cellular telephony has provided a tremendous boost to work productivity and has also allowed the development of social networks in ways not imagined just a few decades ago. The cellular industry has made impressive strides in the introduction of advanced voice and data services. Cellular penetration has reached in some countries very high levels, and it is not uncommon in these countries to see elementary school children carry their personal phone. On the other hand, in many countries only a small part of the population enjoys the benefits of anytime and anywhere communication. Cellular

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operators and equipment manufacturers still face many challenges on how to make cellular telephony available and affordable to many more segments of the world population. Glossary 1st Generation 2nd Generation 2.5 Generation 3rd Generation 3G Partnership Project 3G Partnership Project 2 Authentication, Authorization, and Accounting Advanced Mobile Phone Service American National Standards Institute Application Program Interface Application Server Asynchronous Transfer Mode Base Station Subsystem Base Transceiver Subsystem CDMA Development Group Call Detail Record Code Division Multiple Access Cellular Digital Packet Data Compact HTML Core Network Circuit Switched Call Service Control Function Enhanced Data rates for GSM Evolution European Telecommunications Standard Institute Federal Communications Commission Frequency Division Multiple Access GSM/EDGE Radio Access Network Gateway GPRS Support Node General Packet Radio Service Global Positioning System Global System for Mobile Communication Handheld Device Markup Language Home Location Register Hypertext Markup Language High-Speed Circuit Switched Data Interrogating CSCF Integrated Digital Enhanced Network Internet Engineering Task Force Instant Message IP Multimedia Subsystem International Mobile Telecommunications 2000 Internet Protocol

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1G: 2G: 2.5G: 3G: 3GPP: 3GPP2: AAA: AMPS: ANSI: API: AS: ATM: BSS: BTS: CDG: CDR: CDMA: CDPD: cHTML : CN: CS: CSCF: EDGE: ETSI: FCCv FDMA: GERAN: GGSN: GPRS: GPS: GSM: HDML HLR: HTML: HSCSD: I-CSCF: iDEN: IETF: IM: IMS: IMT-2000: IP:

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Internet Service Provider International Telecommunications Union Location Measurement Unit Mobile IP MPEG-1 Audio Layer 3 Moving Pictures Expert Group Mobile Switching Centre Multimedia Messaging Mobile Terminal Narrow AMPS Nordic Mobile Telephone Open Mobile Alliance Packet Core Network Proxy CSCF Packet Data Network Packet Data Protocol Packet Data Serving Node Push Initiator Public Land Mobile Network Push-to-Talk over Cellular Push Proxy Gateway Packet Switched Public Switched Telephone Network Push-To-Talk Quality of Service Radio Access Network Radio Frequency Radio Network Controller Radio Network System Serving-CSCF Subscriber Identity Module Session Initiation Protocol Serving GPRS Support Node Service Level Agreement Specialized Mobile Radio Short Message Service SMS Serving Centre Short Message Transport Protocol ITU Signalling System number 7 Total Access Communications System Transmission Control Protocol Telecommunications Industry Association Time Division Multiple Access User Datagram Protocol Universal Mobile Telecommunication System Uniform Resource Identifier Universal Resource Locator Universal Serial Bus

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ISP: ITU: LMU: MIP: MP3: MPEG: MSC: MMS: MT: NAMPS: NMT: OMA: PCN: P-CSCF: PDN: PDP: PDSN: PI: PLMN: PoC: PPG: PS: PSTN: PTT: QoS: RAN: RF: RNC: RNS: S-CSCF : SIM: SIP: SGSN: SLA: SMR: SMS: SMS-SC: SMTP: SS7: TACS: TCP: TIA: TDMA: UDP: UMTS: URI: URL: USB:

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TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

USIM: U-TDOA: UTRA: UTRAN: VLR: VoIP: WAP: W-CDMA: WML: XHTML: XHTML-MP:

Universal SIM Uplink Time Difference of Arrival UMTS Terrestrial Radio Access UMTS Terrestrial Radio Access Network Visitor Location Register Voice over IP Wireless Application Protocol Wideband CDMA Wireless Markup Language Extensible HTML XHTML Mobile Profile

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Bibliography

3GPP, http://www.3gpp.org [the Third Generation Partnership Project (3GPP) is a collaboration of telecommunications standards bodies to produce globally applicable Technical Specifications and Technical Reports for a 3rd Generation Mobile System based on evolved GSM core networks and the radio access technologies that they support] 3GPP TS 03.60, "General Packet Radio Service (GPRS); Service description; Stage 2". [defines the stage2 service description for a General Packet Radio Service (GPRS), a packet-mode technique to transfer data on GSM] 3GPP TS 22.228, "Service requirements for the IP multimedia core network subsystem". [this specification defines the service requirements from users’ and operators’ perspective for the support of IP multimedia applications such as speech communication, real time multimedia applications, shared online whiteboards, etc.] 3GPP TS 23.002, “Technical Specification Group Services and Systems Aspects; Network architecture”. [presents the possible architectures of the Universal Mobile Telecommuncation System (UMTS)] 3GPP TS 23.040, “Technical realization of the Short Message Service (SMS)”. [describes the Short Message Service (SMS) for GSM/UMTS networks]

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3GPP TS 23.207, "End-to-end QoS concept and architecture". [provides the framework for end-to-end Quality of Service involving GPRS and includes aspects of interworking to the IM subsystem as well as PSTN and other networks] 3GPP TS 23.228, “IP multimedia subsystem; Stage 2”. [defines the stage-2 service description for the IP Multimedia Core Network Subsystem (IMS), which includes the elements necessary to support IP Multimedia (IM) services] 3GPP TR 23.804, “Support of SMS and MMS over generic 3GPP IP access”. [investigates solutions for providing 3GPP messaging services across WLAN, and, more generically across any form of IP access that is part of the 3GPP system] 3GPP TS 31.102, “Universal Subscriber Identity Module (USIM) application”. [defines the Universal Subscriber Identity Module (USIM) application. This application resides on an integrated circuit card] 3GPP2, http://www.3gpp2.org [the Third Generation Partnership Project 2 (3GPP2) is a collaborative third generation (3G) telecommunications specifications-setting project comprising North American and Asian interests developing global specifications for ANSI/TIA/EIA-41 Cellular Radio Telecommunication] 3GPP2, S.R0005-B v1.0, “Network Reference Model for cdma2000 Spread Spectrum Systems”. [recommends the basic 3GPP2 Wireless Network Reference Model of network entities and associated reference points]

©Encyclopedia of Life Support Systems (EOLSS)

TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

3GPP2, S.R0079-A, “Support for end-to-end QoS”. [describes the requirements necessary to support endto-end quality-of-service (QoS) in the cdma2000 wireless IP network by leveraging, and extending where applicable, the standard IETF protocols for QoS] C. Anderson, (2001) “GPRS and 3G wireless applications”, John Wiley. [describes the GPRS and 3G cellular networks and the development of applications for these networks] A. Pashtan, (2005) “Mobile web services”, Cambridge University Press [describes the key network elements, software components, and software protocols that are needed to realize mobile Web services, including the concept of user context and its potential to create personalized services] CDG: The CDMA Development Group, http://cdg.org [the CDMA Development Group (CDG) is an international consortium of companies who have joined together to lead the adoption and evolution of 3G CDMA wireless systems]

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IETF RFC 2002, “IP Mobility Support”. [specifies protocol enhancements that allow transparent routing of IP datagrams to mobile nodes in the Internet] IETF RFC 3261, “SIP: Session Initiation Protocol”. [describes SIP, an application-layer control protocol for creating, modifying, and terminating sessions with one or more participants for Internet telephone calls, multimedia distribution, multimedia conferences, etc.] International Engineering Consortium (http://www.iec.org), “Billing in a 3G environment” [examines the challenges that service providers face in deploying billing systems that support the evolution from 2G to 3G cellular services] M. Mouly & M.B. Pautet, (1992) “The GSM system for mobile communications”, Mouly and Pautet. [describes the GSM standard for mobile stations, switching equipment, radio interface, transmission methods, and signaling protocols] Open mobile alliance, http://www.openmobilealliance.org/ [the Open Mobile Alliance (OMA) is an industry forum to facilitate global user adoption of mobile data services by specifying market driven mobile service enablers that ensure service interoperability] M. Pipikakis, (2004) “Evaluating and improving the quality of service of second generation cellular systems”, Bechtel Telecommunications Technical Journal, v.2, n.2. [describes network performance management and quality of service (QoS) of matured second generation (2G) cellular systems]

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R. Koodli & M. Puuskari, (2001) “Supporting Packet-Data QoS in Next-Generation Cellular Networks”, IEEE Communications, Feb. 2001 (http://www.comsoc.org/ci1/private/2001/feb/koodli.html) [describes the packet data quality-of-service (QoS) architecture and specific mechanisms that are being defined for multi-service QoS provisioning in the Universal Mobile Telecommunication Systems (UMTS)] Biographical sketch

Ariel Pashtan, Ph.D., is President of Aware Networks, Inc., Illinois, USA (http://awarenetworks.com). He is a network applications consultant and develops service oriented architectures and wireless web services for cellular systems. Ariel has over 20 years of industry experience working for Motorola, IBM, Gould, and Israel Aircraft Industries. He was a distinguished member of the technical staff in Motorola Labs where he managed research projects. His past experience includes leading wireless Web services architecture research, and cellular network management requirements and standards teams. Past academic appointments include teaching at Northwestern University and the Technion - Israel Institute of Technology. Ariel is the author of "Mobile Web Services", Cambridge University Press, 2005. He published journal and conference papers on wireless networks and software architecture and design, and holds several U.S. patents. Ariel is a senior member of the IEEE.

To cite this chapter Ariel Pashtan, (2007), WIRELESS TERRESTRIAL COMMUNICATIONS: CELLULAR TELEPHONY, in Telecommunication Systems and Technologies , [Ed. Paolo Bellavista], in

©Encyclopedia of Life Support Systems (EOLSS)

TELECOMMUNICATION SYSTEMS AND TECHNOLOGIES – Wireless Terrestrial Communications: Cellular Telephony Ariel Pashtan

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Encyclopedia of Life Support Systems (EOLSS), Developed under the Auspices of the UNESCO, Eolss Publishers, Oxford ,UK, [http://www.eolss.net]

©Encyclopedia of Life Support Systems (EOLSS)