Introduction To Pan

1.0 INTRODUCTION 1.1 Background In recent years, there have been substantial developments in the acceptance and functionality of wireless networks. Organisations are finding their workforce increasingly mobile, often equipped with notebook computers and spending more of their productive time working away from the standard office-desk or personal-computer environment. More often than not, many workers find cables to be a hassle as cables get lost or damaged easily and they add unnecessary bulk and weight when carried around. Wireless network has been able to solve the problem as wireless networks support mobile workers by providing the required freedom in their network access. Working wirelessly also allows these workers to access networked resources from any point within the range of a wireless access point. For Information Technology managers, the combination of lowering wireless hardware costs and the ease of implementation into diverse office environments means that wireless deployment is actively promoted, for it provides the combination of wired network throughput with mobile access and configuration flexibility. Thus, it has becomes quite desirable to develop connectivity solutions for interconnecting personal devices that do not require the use of cables.

1.2 Objective Going wireless has its disadvantages. There has been discussion about the problems of interoperation, backwards compatibility and interference between the various technologies. The most prevalent WLAN technology, Wi-Fi which operates within the crowded 2.4 GHz ISM band brings about the problem of interference between Wi-Fi and Bluetooth. Researches done on this interference issue have concluded that, when 1

separated by two metres or more, there appears to be no significant interference. However, when the separation distances is less than two metres, the two technologies can interfere with each other and this can cause severe problems when collocated within a single device. Several solutions have already been proposed, ranging from modifications and extensions to the existing standards, through recommended best practices and technological advances. The 802.15.3 standard has been recently approved by IEEE as a high data rate WPAN. This new standard would be able to bring WPAN to greater heights as it would be able to provide the foundation for a broad range of interoperable consumer devices by establishing universally adopted standards for wireless digital communication. The objective of the 802.15.3 is to rapidly create a consensus standard that has broad market applicability and deals effectively with the issues of coexistence with other wireless networking solutions. 802.15.3 is not an extension of 802.15.1 because the MAC is different. This project attempts to investigate the compatibility of at least the coexistence of 802.15.3 with other systems, especially those in similar market spaces, such as Bluetooth.

1.3 Report overview The report will attempt to discuss the design and operating characteristics of the Bluetooth voice transmission and 802.15.3. This report will first give an overview of the Bluetooth technology as well as that of 802.15.3. Subsequently, a modelling and simulation of the Bluetooth voice transmission and the operating characteristics of 802.15.3 using the MATLAB software package will be presented. The results of the Bluetooth voice transmission will also be presented and analysed, together with the 2

analysis for the operating characteristics of 802.15.3. Finally, recommendations and conclusions on the results will be made.

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2.0 BLUETOOTH 2.1 Overview Bluetooth SIG was founded in 1998 when several telecommunications and computing companies noticed that there was a need for a wireless technology to connect portable devices such as laptops and mobile phones. As infrared technology had its limitations, thus, a technology based on radio links was conceived. To avoid the chaos of incompatible proprietary solutions, the major telecommunications and computing companies, Nokia, Ericsson, IBM, Intel and Toshiba decided to create a common standard for wireless connectivity called Bluetooth. The consortium, Bluetooth SIG was established to create and publish specifications, promote the technology and administer a qualification program to ensure interoperability. Bluetooth was designed to allow low bandwidth wireless connections to become simple to use to be integrated into daily life. It uses a short-range radio link that has been optimised for power-conscious, battery-operated, small size, lightweight personal devices. An example of a Bluetooth application is the updating of phone directory of the mobile phone. Today, one would have to either manually enter the names and phone numbers of all contacts or use a cable or IR link between the phone and the PC and start an application to synchronise the contact information. With Bluetooth, this could all happen automatically and without any user involvement as soon as the phone comes within range of the PC.

2.2 Purpose Bluetooth technology was invented to replace cables between small personal devices

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such as mobile phones, pagers, PDAs (refer to Figure 2.1). As such, Bluetooth wireless technology is optimised for short-range, low-power, voice and data communication. Although some Bluetooth profiles describe methods to connect personal devices to networks, Bluetooth technology is not a bona fide networking technology. In contrast to WLAN technologies such as IEEE 802.11, Bluetooth wireless communications consume significantly less power because Bluetooth links operate over shorter distances and at lower data rates. The nominal data rate and range for Bluetooth technology are each about one-tenth that of the IEEE 802.11. Although this does not necessarily mean that Bluetooth communication uses only 1 percent of the power required for WLAN communication, it does indicate that significantly less power is required for Bluetooth communications.

Figure 2.1: Bluetooth environment (Sturman 2003)

2.3 WPAN architecture A Bluetooth WPAN is created in an ad-hoc manner whenever an application in a device desires to exchange data with matching applications in other devices. The Bluetooth 5

WPAN ceases to exist when the applications involved have completed their tasks and is no longer need for the exchange of data. Bluetooth devices use FHSS, moving through 1,600 different frequencies per second or 625us per frequency hop to reduce interferences and fading. There are 79 or 23 RF channels of 1MHz with a symbol rate of 1Mbps Radio power between 0 and 20 dBm. A typical Bluetooth device has a range of about 10 metres. Bluetooth devices use TDMA scheme where the master starts its transmission in even numbered slots only, whereas the slave starts its transmission solely in odd numbered slots. On the channel, information is exchanged through packets. Each packet is transmitted on a different frequency in the hopping sequence. A packet nominally covers a single slot, although it can be extended up to either three or five slots. A Bluetooth WPAN supports both synchronous communication channels for telephonygrade voice communication and asynchronous communications channels for data communications. The supported channel configurations are as shown in Table 2.1.

Configuration

Max. Data Rate

Max. Data Rate

(Upstream)

(Downstream)

64 kb/sec X 3 channels

64 kb/sec X 3 channels

Symmetric Data

433.9 kb/sec

433.9 kb/sec

Asymmetric Data

723.2 kb/sec

723.2 kb/sec

or 57.6 kb/sec

or 57.6 kb/sec

3 Simultaneous Voice Channels

Table 2.1: Channel configuration (Blankenbeckler n.d.) The synchronous voice channels are provided using circuit switching with a slot reservation at fixed intervals while the asynchronous data channels are provided using

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packet switching utilising a polling access scheme. A combined data-voice SCO packet is also defined and can provide 64 kb/sec voice and 64 kb/sec data in each direction.

2.3.1 The Bluetooth WPAN piconet A piconet is a WPAN formed by a Bluetooth device serving as a master in the piconet with one or more Bluetooth devices serving as slaves. Each piconet is defined by the address of the master based on a frequency-hopping channel. All devices participating in communications in a given piconet are synchronised to the frequency-hopping channel for the piconet, using the clock of the master of the piconet. Usage scenarios may dictate that certain devices act always as masters or slaves. However, a slave device could be used as a master during one communications session and vice versa. Slaves communicate only with their master in a point-to-point fashion under the control of the master while the master’s transmissions may be either point-to-point or point-tomultipoint. Multiple piconets with overlapping coverage areas form a scatternet.

2.3.2 The Bluetooth WPAN scatternet A scatternet is a collection of operational Bluetooth piconets overlapping in time and space. A Bluetooth device may participate in several piconets at the same time, thus allowing for the possibility that information could flow beyond the coverage area of the single piconet. A Bluetooth unit can act as a slave in several piconets but only as a master in a single piconet. To participate on the proper channel, it should use the associated master device address and proper clock offset to obtain the correct phase. Figures 2.2 and 2.3 show the various ways Bluetooth devices interconnect to form a communicating system.

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Figure 2.2: A piconet (Blankenbeckler n.d.)

S

M S

M S

S S S

M

Master

S

Slave

Figure 2.3: Scatternet consisting of 2 piconet (Tzamaloukas n.d.)

2.4 Physical layer The PHY is the first layer of the seven-layer OSI model and is responsible for transmitting bits over adjacent system over the air. Bluetooth operates in the 2.4 GHz ISM band. In a majority of countries around the world, the range of this frequency band

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is between 2400 MHz to 2483.5 MHz. In the United States and Europe, a band of 83.5 MHz width is available with 79 RF channels spaced 1 MHz apart being defined. France, on the other hand has a smaller band with 23 RF channels spaced 1 MHz apart being defined.

2.4.1 Transmitter characteristic Each device is classified into three power classes, namely Power Class 1, 2 and 3. 1. Power Class 1 is designed for long range (approximately 100m) devices, with a maximum output power of 20 dBm, 2. Power Class 2 is for ordinary range devices (approximately 10m) devices, with a maximum output power of 4 dBm, 3. Power Class 3 is for short range devices (approximately 10cm) devices, with a maximum output power of 0 dBm. The Bluetooth radio interface is based on a nominal antenna power of 0dBm and each device can optionally vary its transmitted power.

2.4.2 Modulation The Bluetooth radio module uses GFSK where a binary one is represented by a positive frequency deviation and a binary zero, by a negative frequency deviation. Bluetooth bandwidth time is set to 0.5 and the modulation index must be between 0.28 and 0.35.

2.4.3 Receiver characteristic 2.4.3.1 Sensitivity level The receiver must have a sensitivity level for which the bit error rate 0.1 percent is met. For Bluetooth this means an actual sensitivity level of -70dBm or better.

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2.4.3.2 Interference performance The interference performance on Co-channel and adjacent 1 MHz and 2 MHz are measured with the wanted signal 10 dB over the reference sensitivity level. On all other frequencies, the wanted signal should be 3 dB over the reference sensitivity level. If the frequency of an interfering signal lies outside the band of 2400 MHz to 2497 MHz, the out-of-band blocking specification shall apply.

2.4.3.3 Out-of-band blocking The out-of-band blocking is measured with the wanted signal 3 dB over the reference sensitivity level and the interfering signal shall be a continuous wave signal. The BER shall be less than or equal to 0.1 percent and the out-of-band blocking should fulfil the requirements as stated in Table 2.2.

Interfering Signal frequency (GHz)

Interfering Signal Power (dBm)

0.030 – 2.000

-10

2.000 – 2.399

-27

2.498 – 3.000

-27

3.000 – 12.750

-10

Table 2.2: Out of band blocking requirements (IEEE 802.15.1 2002)

2.5 Baseband layer The baseband layer lies on top of the Bluetooth physical layer in the Bluetooth stack. The baseband protocol is implemented as a link controller, which works with the link manager for the carrying out of link level routines such as link connection and power

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control. The baseband also manages asynchronous and synchronous links, handles packets and does paging and inquiry to access and inquire Bluetooth devices in the area. For full duplex transmission, a Time-Division Duplex scheme is used. On the channel, information is exchanged through packets with each packet being transmitted on a different hop frequency. A packet nominally covers a single slot, but can be extended to cover up to five slots.

2.5.1 Packets Thirteen different packet types are defined for the baseband layer of the Bluetooth system. All higher layers use these packets to compose higher level PDU's. The ID, NULL, POLL, FHS, DM packets are defined for both SCO and ACL links while the DH, AX1, DM3, DH3, DM5, DH5 packets are defined for ACL links only and the HV1, HV2, HV3, DV for SCO links only. Each packet consists of three entities, namely the access code (68/72 bits), the header (54 bits) and the payload (0-2745 bits) as shown in Table 2.3.

Table 2.3: Standard packet format (Nokia 2003) The first entity, the access code are used for timing synchronisation, offset compensation, paging and inquiry. There are three different types of access code, namely Channel Access Code (CAC), Device Access Code (DAC) and Inquiry Access Code (IAC). The channel access code identifies a unique piconet and the DAC is used for paging while

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the IAC is used for inquiry purpose. The second entity, the header contains information for packet acknowledgement, packet numbering for out-of-order packet reordering, flow control, slave address and error check for header. The third entity, the packet payload can contain either voice field, data field or both. It has a data field and the payload will also contain a payload header.

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3.0 IEEE 802.15.3 3.1 Overview The IEEE 802.15 Working Group, a part of the IEEE 802 LAN/MAN Standards Committee, develops the Personal Area Network consensus standards for short distance wireless networks known as WPAN. These WPANs address wireless networking of portable and mobile computing devices such as PCs, PDAs, peripherals, cell phones, pagers and consumer electronics; allowing these devices to communicate and interoperate with one another. The 802.15 Working Group also develops low-power standards for personal area networks with long battery life and low cost requirements. Some of the interesting sub-groups include: 1. 802.15.1, a derivative of Bluetooth 2. 802.15.2 offers similar abilities to those of Bluetooth and 802.15.1, but it is designed to coexist with 802.11b, WLAN without causing interference 3. 802.15.3 aims to increase the data rate similar to those of Bluetooth and 802.15.1. The target was originally 20Mbit/sec. 4. 802.15.3a is follow-on of 802.15.3 and it support up to 110 Mbps. 5. 802.15.4 is a low power version, with low data rate and long battery life. It is intended for smart card, security tag and other embedded devices (Khirat & Kadhi 2002). IEEE 802.15.3 was designed to enable wireless connectivity of high-speed, low-power, low-cost, multimedia-capable portable consumer electronic devices. This standard provides data rates from 11 to 55 Mb/s at distances of greater than seventy metres while maintaining quality of service (QoS) for the data streams. It also addresses the QoS capabilities required to support multimedia data types and focuses on power

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management, quality of service and security. Additionally, this standard is designed to provide simple, ad-hoc connectivity similar to Bluetooth that allows the devices to automatically form networks and exchange information without the direct intervention of the user. Products compliant with this standard will complement, not compete with, products compliant with IEEE 802.11, because 802.11 is a standard for Local Area Networks, and 802.15.3 will be a standard for Personal Area Networks. The difference is similar to that in the wired world of Ethernet and USB or Firewire, which provide for connectivity to the network and to peripheral devices respectively (Dornan 2002). As Bob Heile of IEEE 802.15 (cited in IEEE 2004), pointed out, “One of the major goals for 802.15, as well as for the Bluetooth SIG, is global use of WPAN technology. The 802.15.3 standard allows networks based on this specification to coexist with other 802.15 WPANs, such as Bluetooth systems, and with 802.11 WLANs, especially 802.11b and 802.11g, which also operate in the 2.4-GHz band. Devices using IEEE 802.15.1 WPAN and Bluetooth technology will provide country-to-country usage for travellers. They will be able to be used in cars, airplanes and boats on a global basis”.

3.2 Purpose A goal of this standard will be to achieve a level of interoperability or coexistence with other 802.15 standards. It is also the intent of this standard to work towards a level of coexistence with other wireless devices in conjunction with coexistence task groups such as 802.15.2. Based on the previous calls for applications collected for 802.15, there remains a significant group of applications that could not be addressed by 802.15.1. High data

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rates are required for time dependent and large file transfer applications such as video or digital still imaging, without sacrificing the requirements of 802.15.3. 20 Mb/s is proposed to be the lowest rate for these types of data. It is not and extension of 802.15.1, because the MAC needs are different. The purpose of 802.15.3 is to provide for low complexity, low cost, low power consumption that are comparable to the goals of 802.15.1 and high data rate wireless connectivity among devices within or entering the personal operating space. The data rate is high enough, 20 Mb/s or more, to satisfy a set of consumer multimedia industry needs for WPAN communications (IEEE 802.15.3 2003).

3.3 Communication environment WPANs are used to convey information over relatively short distances among a relatively few participants. Unlike WLANs, connections effected via WPANs involve little or no infrastructure. This allows small, power efficient, inexpensive solutions to be implemented for a wide range of devices. The data rate must be high enough, that is, greater than 110 Mbps, to satisfy a set of consumer multimedia industry needs for WPAN communications. It uses time division multiple access to allocate channel time among devices to prevent conflicts and only provides new allocations for an application if enough bandwidth is available. Devices included in the definition of PAN are those that are carried, worn or located near the body. Specific examples of devices include those that are thought of as traditionally being networked, such as computers, PDAs, handheld personal computers,

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and printers. Other devices include digital imaging systems, microphones, speakers, headsets, bar code readers, sensors, display and pagers.

3.3.1 Piconet A piconet is a set of devices within a personal operation space operating under the control of a PNC in order to share a wireless resource. The PNC always provides the basic timing for the WPAN. Additionally, the PNC manages the QoS requirements of the WPAN. This wireless ad-hoc communication covers at least ten metres in all directions and envelops the person or a thing, whether stationary or in motion. This standard allows a device to request the formation of a subsidiary piconet. The original piconet is referred to as the parent piconet while the subsidiary piconet is referred to as either a child or neighbour piconet, depending on the method the DEV is used to associate with the parent PNC. Child and neighbour piconets are also referred to as dependent piconets since they rely on the parent PNC to allocate channel time for the operation of the dependent piconet. An independent piconet is a piconet that does not have any dependent piconets. Parent and child piconets share common frequency channel while an independent piconet is either far enough apart or on different frequency channel and operates independently of other piconets. Child piconet controller can exchange data with parent piconet controller while a neighbour piconet controller only shares frequency channel. Unassociated device listens for presence of other piconets and associates with existing piconet or forms independent, child or neighbour piconet depending on directives from host controller and presence of other piconets (refer to Figure 3.1).

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Parent Piconet Controller Piconet Device Child/Neighbour Piconet Controller Piconet Relationship

Peer to Peer Data Transmission Independent Piconet Controller

Figure 3.1: A WPAN topology (Barr 2002)

3.4 MAC layer IEEE 803.15.3 MAC is designed to support the fast connection, ad-hoc networks, quality of service with data transport, security, channel robust for multimedia traffic over the WPAN and peer to peer communication. The device in the piconet are able to employ power saving techniques to reduce their power consumption.

3.4.1 Superframe Superframe #m

Superframe #m-1

Beacon #m

Contention Access Period

Superframe #m+1

Channel Time Allocation Period MCTA 1

MCTA 2

CTA 1

CTA 2

CTA n-1

Figure 3.2: Superframe structure (IEEE 802.15.3 2003)

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CTA n

Channel time in the 802.15.3 piconet is divided into a superframe, which is illustrated in Figure 3.2. The superframe is composed of three parts, namely the beacon, contention access period and the channel time allocation period. The beacon, which is used to set the timing allocations and to communicate management information for the piconet consists of the beacon frame, as well as any Announce commands sent by the PNC as a beacon

extension.

The

contention

access

period

(CAP)

is

used

for

authentication/association for request/response while the channel time allocation period (CTAP), which consist of CTAs, and MCTAs. CTAs are used for commands, isochronous streams and asynchronous data connections. The length of the CAP is determined by the PNC and communicated to the devices in the piconet via the beacon. However, the PNC is able to replace the functionality provided in the CAP with management CTAs, except in the case of the 2.4 GHz PHY, where the PNC is required to allow the device to use the CAP. MCTAs are a type of CTA that is used for communications between the devices and the PNC. The CAP uses CSMA/CA for the medium access. The CTAP, on the other hand, uses a standard TDMA protocol where devices have specified time windows. MCTAs, are either assigned to a specific source or destination pair and use TDMA for access or they are shared CTAs that are accessed using the slotted aloha protocol.

3.5 Physical layer The PHY operates in the 2.4 – 2.4835 GHz frequency range. It specifies raw data rates of 11, 22, 33, 44 and 55M bit/sec, with the respective modulation type QPSK, DQPSK, 16-QAM, 32-QAM, and 64-QAM. The base rate of 22M bit /sec is uncoded while 11, 33,

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44 and 55M bit/sec use trellis coded modulation. Distance plays a role in transmission speed. The closer the device is to the access point, the higher the bandwidth. For instance, a device up to fifty metres away from an access point can transmit data at a speed of 55M bit/sec, while the transmission speed of a device one hundred metres away drops to 22M bit/sec. The highest rate, 55M bit/sec, is necessary for low-latency, multimedia connections and large-file transfers, while 11M bit/sec and 22M bit/sec rates are ideal for long-range connectivity for audio devices (Barr 2002).

3.5.1 Channels The on-air bandwidth is limited to 15 MHz in order to allow more channels as well as to decrease the interference to other systems and to decrease the susceptibility to interference from other systems. The transmit power is approximately 8dBm. A total of five channels in two sets are assigned for operation. The first set allocates four channels for high-density application while the second allocates three channels to enable better co-existence with IEEE Std 802.11b -1999. Since the two outer channels of the sets overlap, there are a total of five channels allowed for operation. The assigned channels are shown in Table 3.1. A compliant 802.15.3 implementation shall support all five channels.

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CHNL_ID

Centre frequency

High-density

802.11b coexistence

1

2.412 GHz

X

X

2

2.428 GHz

X

3

2.437 GHz

4

2.445 GHz

X

5

2.462 GHz

X

X

X

Table 3.1: GHz channel plan (IEEE 802.15.3 2003) A device may, in the course of a scan, change to an 802.11b channel for the purpose of detecting the presence of 802.11b networks. When a device is scanning to start a piconet, it should scan all five channels to decrease the probability of choosing an occupied channel. If a device is capable of identifying an 802.11b network and it does identify an 802.11b network while scanning, it should use the 802.11b coexistence channel set. It should also rate the channels where 802.11b networks were identified as the worst channels. If multiple 802.11b networks are detected, the device should order them based on an estimate of the amount of traffic and the power level in the channel.

3.5.2 Modulation and coding The 2.4-GHz physical layer standard specifies uncoded DQPSK modulation as well as QPSK, 16/32/64-QAM with trellis coding (refer to Figure 3.3). An 802.15.3-compliant DEV shall, at a minimum, support DQPSK modulation. In addition, if an 802.15.3 DEV supports a given modulation format other than DQPSK, it shall also support all of the lower modulation formats. For example, if an 802.15.3 implementation supports 32-

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QAM, it shall also support 16-QAM and QPSK-TCM as well as the DQPSK modulation formats.

64-QAM TCM (55 Mbit/s) 32-QAM TCM (44 Mbit/s)

16-QAM TCM (33 Mbit/s)

DQPSK, QPSK (22 Mbit/s uncoded, 11 Mbit/s coded)

Figure 3.3: DQPSK, QPSK, 16/32/64 QAM signal constellations (IEEE 802.15.3 2003)

3.5.2.1 DQPSK modulation No coding shall be applied to the DQPSK modulation. The mapping of the bit pairs to DQPSK symbols shall be implemented as specified in Table 3.2. In Table 3.2, phase change shall be defined as a counter clockwise rotation. The differential encoding applies only to the DQPSK mode. In this mode, the entire frame, with the exception of the PHY preamble shall be encoded differentially.

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Bit pattern d0, d1

Phase change

0,0

0

0,1

π/2

1,0

π

1,1

-π/2

Table 3.2: DQPSK encoding table (IEEE 802.15.3 2003)

3.5.3 Base data rate The base data rate of the 802.15.3, 2.4-GHz PHY shall be 22 Mb/s operating in the uncoded DQPSK mode. The DQPSK mode is used as a base rate instead of the 11 Mb/s QPSK-TCM mode to reduce the overhead due to the duration of the PHY and MAC headers. Also, DQPSK capability is necessary to implement the PHY preamble.

3.6 Coexistence, interoperability and interference Coexistence, in this context, refers to the co-location of IEEE P802.15.3 devices with other, non-802.15.3 devices. The criteria described in this section focuses only on the impact the 802.15.3 devices have on other non-P802.15.3 devices that may be sharing the same frequency bands. The following IEEE wireless protocols are allowed to operate in an operational area that overlaps with the operational area of an 802.15.3 piconet, but could experience reduced throughput: 1. 802.11 DSSS 2. 802.11 FHSS 3. 802.11b

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4. 802.15.1 with some networks, the throughput could be reduced and so under certain conditions, overlapping operation might be undesirable.

3.6.1 Interoperability with 802.11b 802.11b and 802.15.3 share the same frequency band, which makes interoperability of radio modules much simpler and cheaper. Additionally, the 802.15.3 PHY layer uses 11 Mbaud, DQPSK modulation for the base rate, which is the same as the chip rate and modulation for 802.11b. However, 802.11b uses either a Barker code, CCK or PBCC as a spreading code, which is not a part of the 802.15.3 standard. The 802.15.3 PHY was also chosen with the same frequency accuracy, allowing the reuse of reference frequency source and frequency synthesisers. While the 802.11b and 802.15.3 frequency plans are slightly different, the synthesisers that would normally be used in either radio would be capable of 1 MHz frequency step size and so would be capable of supporting either frequency plan. The RX/TX turnaround time is also the same for both protocols (Gilb 2001). However, the TX/RX turnaround for 802.11b is 5 micro seconds versus a 10 micro seconds for 802.15.3, which could have an impact on the architecture of a dualmode radio. Thus, the similarities between 802.15.3 and 802.11b are as follows: 1. DQPSK modulation 2. 11 MBaud symbol (chip) rate. 3. Frequency and symbol timing accuracy of +/- 25 ppm. 4. RX/TX turnaround time 5. Power ramp up/down Some of the differences include:

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1. Barker, CCK or PBCC spreading code 2. Power spectral density 3. Frequency plan 4. Performance criteria 5. TX/RX turnaround time. 6. PHY preamble, header, frame structure 7. MAC

3.6.2 Coexistence with 802.11b The 802.15.3 PHY faces two problems in coexisting with 802.11b. 1. Both use the same frequency range 2. 802.11b uses CSMA/CA and a polling method with the point coordination function while 802.15.3 uses a hybrid CSMA/CA and TDMA. 802.15.3 piconets use two access methods in the superframe; CSMA/CA during the CAP and TDMA during the CTAP. The CAP provides the best method of coexistence with 802.11b networks, since the CSMA/CA algorithm used in the CAP is similar to the CSMA/CA algorithm used in 802.11b, that is, the transmitter uses a listen-before-talk mechanism. In the case of 802.11, there is more than one CCA method allowed and some of them would not recognise an 802.15.3 frame. In this case, the 802.11b transmission might collide with 802.15.3 frames. However, an 802.11b station which implemented ‘energy above threshold’ for CCA, that is, CCA mode 1 or CCA mode 5, would signal that the medium is busy when a sufficiently strong 802.15.3 signal is present. The 2.4 GHz PHY

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of 802.15.3 requires energy detection as a part of the CCA process. A sufficiently strong 802.11b signal would result in the 802.15.3 DEV signalling that the medium is busy, which would improve the coexistence performance. A sufficiently strong 802.11b signal would result in the 802.15.3 DEV signalling that the medium is busy, which would improve the coexistence performance.

3.7 Comparisons between the two standards A comparison between some characteristics of the IEEE 802.15.3 and Bluetooth is given by Table 3.3 below.

Bluetooth

802.15.3

Centre frequency

2.4 GHz

2.4 GHz

Baud rate

1 MHz

11 MHz

Modulation

GFSK

DQPSK

Tx Power

0 dBm

0 dBm

Rx Antenna Gain

0 dBi

0 dBi

Rx Sensitivity

-70 dBm

-75 dBm

Range

10m

10m

No of video channel

0

5

Cost

Low

Medium

Regional support

World wide

World wide

Target application

Voice + data

Voice + data + multi media

Piconet structure

1 PNC, ≤ 255 1 master, ≤ 7 slaves active nodes

Table 3.3: Bluetooth versus 802.15.3 (Adapted from IEEE 802.15.1 2002, IEEE 802.15.3 2003)

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From this table, it is clear that the 802.15.3 WPAN operates in a more daunting intimidating environment than Bluetooth, in terms of required capabilities. From a security perspective, the operating environments are, however, quite similar.

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4.0 SIMULATION RESULTS 4.1 Bluetooth voice transmissions The Bluetooth Voice Transmission, models part of a Bluetooth system. Bluetooth is a short-range radio link technology that operates in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band. The model modulates the signal using Gaussian frequency shift keying (GFSK) over a radio channel with maximum capacity of 1Mbps. The Simulink model modelled transmission of Synchronous Connection Oriented (SCO) voice packets HV1, HV2 and HV3. It covers the signal processing characteristics of the baseband section of the Bluetooth specification and some of the radio section. This includes typical physical layer components, such as speech processing, framing, coding, modulation, and frequency hopping, which are implemented in digital hardware or DSP software. The physical layer of a communication system is ideally represented as a block diagram and this is why Simulink is an appropriate tool for developing this model (McGarrity 2001). Bluetooth voice transmission uses synchronous connection-oriented packets to provide full-duplex voice communication between two devices. The timing of voice and data transmission is organised around a slot framework. Each slot is 625 microseconds long, with six slots defining an SCO period. As voice is transmitted at 64 Kbits/second, 240 bits are required to be transmitted during each SCO period. The high-quality voice (HV) packet types differ according to how much forward error correction (FEC) coding they use. The packet types range from HV1, employing one-third repeat coding and transmitting every second slot, to HV3, employing no coding and transmitting every sixth slot.

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Interoperability of wireless devices is a growing concern, due to the rise in popularity of systems using unlicensed bands, spread spectrum and frequency hopping. One particular area of investigation is Bluetooth and 802.11b, which share the 2.4-GHz ISM band. Interference can occur when Bluetooth and 802.11b devices are in close proximity, and the Bluetooth frequency hops to within the 22-MHz 802.11b channel while the 802.11b device is transmitting. For example, if an 802.11b transmitter and a Bluetooth transmitter are equidistant from a Bluetooth receiver, the carrier-to-interference ratio, such as -2 dB, is considerably lower that the 18-dB signal-to-noise ratio usually required for a Bluetooth receiver. The Bluetooth FEC on the header or payload cannot protect the bits and the whole packet can be corrupted. The next packet of voice data will be transmitted at a new hop frequency, usually not in the same vicinity as the 802.11b transmitter. But 802.11b transmission is very different from Bluetooth's. Packets are of variable length and can be more than 4,000 bytes long, equivalent to more than 50 Bluetooth slots. Transmission is asynchronous with the media-access control layer using a carrier-sense multiple-access with collision-avoidance technique similar to that used by Ethernet. The physical layer of 802.11b uses a combination of differential binary phase shift keying, differential quaternary phase shift keying, Barker code spreading and complementary code keying in one of 11 possible overlapping channels, each with a fixed bandwidth of 22 MHz. The transmit power of 802.11b is also higher than Bluetooth's, with a maximum of 1 W in the United States.

4.1.1 Structure of the model The model consists of a master transmitter, radio channel, slave receiver, 802.11.b interferer. The transmitter subsystem performs speech coding, buffering, framing, header

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error control (HEC), forward error correction, GFSK modulation and frequency hopping. Channel effects modelled include thermal noise, path loss and interference. The Free Space Path Loss block, from the RF Impairments library, models path loss. The IEEE 802.11b interferer is a masked subsystem that opens up a mask dialog for user input on double-clicks. Mean packet rate, packet length, power and frequency location in the ISM band can be specified in the mask dialog while the slave receiver recovers speech from the transmitted signal, performing all the complementary operations that the transmitter does, but in reverse order.

4.1.2 Frequency hopping Radio Frequency technology allows devices to be in different rooms or even buildings. The limited range of radio signals restricts the use of this kind of network. RF technology can be on single or multiple frequencies. A single radio frequency is subjected to outside interference and geographic obstructions. Furthermore, a single frequency is easily monitored by others, which makes the transmissions of data insecure. Spread spectrum avoids the problem of insecure data transmission by using multiple frequencies to increase the immunity to noise and to make it difficult for outsiders to intercept data transmissions (Cisco Systems 2003). There are two common forms of spread spectrums, namely direct spectrum, where the data sequence is multiplied by the pseudo noise sequence, and frequency hopping, where the narrowband signal is ‘hopped’ over different carrier frequencies based on the pseudo noise sequence. Both techniques result in a transmit signal bandwidth that is much larger than the original signal bandwidth, hence the name spread spectrum (Walrand & Varaiya 2000, p. 330). The hopping of the carrier produces the desired spreading of the 29

transmitted signal spectrum. The changes in the carrier frequency do not affect the performance in additive noise and the AWGN performance remain exactly the same as the performance of the digitally modulated system without frequency hopping. Just as with DSSS technique, the FHSS technique can allow coexistence of several systems with orthogonal codes in the same frequency band and can provide a degree of user-signal privacy by association of each user’s signal with a randomly selected hopping pattern. One difference between the two spreading methods is that the DSSS technique uses the full system bandwidth throughout the entire transmission time whereas FHSS uses only a portion of the band at a time. In a FHSS system, each user employs different hopping pattern; in this system, interference occurs when two different user land on the same hop frequency. If codes are random and independent of one another, the ‘hit’ will occur with some calculable probability. If the codes are synchronised and the hopping patterns selected so that two users never hop to the same frequency at the same time, the multiple user interference is eliminated. Figures 4.1 and 4.2 show the block diagram of a transmitter and receiver for a FHSS system.

Data modulator

Highpass filter

Frequency synthesizer

Carrier frequency 1 FH clock

2

3...

k

Code generator

Figure 4.1: Block diagram of FHSS transmitter (Pahlavan & Levesque 1995, p. 370) 30

Image reject filter

Bandpass filter

Data modulator

Frequency synthesizer

Carrier frequency 1

2

3...

Code generator f

k FH clock

Figure 4.2: Block diagram of FHSS receiver (Pahlavan & Levesque 1995, p. 370) At the transmitter, the digital modulation and the modulation over the hop frequencies are implemented in two stages. The hop frequencies are randomly selected using the frequencies synthesiser controlled by the pseudo noise code generator. A wideband filter is applied to the signal for spectral shaping before the signal is fed to the antenna. The receiver has a wideband front end filter that accommodates the entire system bandwidth. This filter is followed by a pseudo noise code controlled frequency synthesizer synchronized to the frequency synthesizer. After desynthesising, the signal is passed through a noise reduction bandpass filter with the same bandwidth as the transmitted information symbols. The final stage of the receiver is the data demodulator, which modulates the first stage digital modulation (Pahlavan & Levesque 1995, p. 368).

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Energy

5

8

3

7

1

4

6

2

f1

f1

f1

f1

f1

f1

f1

f1 Frequency

Figure 4.3: Channel assignment (Stallings 2004 p. 278) Frequency

f8 f7 f6 f5 f4 f3 f2 f1

Figure 4.4: Channel use (Stallings 2004 p. 278) Figures 4.3 and 4.4 are examples of a frequency hopping signal. A number of channels are allocated for the FH signal. Typically there are 2ª carrier frequencies forming 2ª channels. The spacings between carrier frequencies and hence the width of each channel

32

usually correspond to the bandwidth of the input signal. The transmitter operates in one channel at a time for a fixed interval. The sequence of channel used is dictated by a spreading code. Both transmitter and receiver use the same code to tune into a sequence of channels in synchronisation. Spectrum of the transmitted Bluetooth signal with IEEE 802.11b interference is shown in Figure 4.5. The blue lines are the Bluetooth transmissions, while the red lines are from 802.11b transmission. A dynamic plot of packet frequency versus time is shown by the Spectrogram plot. Most of the time, due to frequency hopping, there is not much overlap of these slots. In a few cases, the signals do collide, as shown by Figure 4.6.

Figure 4.5: Integration of two waveforms

Frequency hopping

Figure 4.6: Spectrogram with collision

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4.1.3 Error rate The error rate display in Figure 4.7 shows three types of error rates, namely, Raw bit error rate, Residual bit error rate and Frame error rate. The raw bit error rate displays the inconsistencies between the bits in the transmitted signal and the received signal while frame error rate refers to the ratio of frame failure to the total number of frames. Frame failure, caused by noise and interference, is determined if the HEC fails to match the header info or if less than 57 bits are correct in the access code. If the frame fails, this is captured by a zero-valued Frame OK signal, which is used in the FER calculation as well as to exclude bad frames from the residual BER calculation.

Figure 4.7: Error rate display

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4.1.4 Additive white gaussian noise The noise in a communication channel exits as unwanted random signal that interferes with the information signal being transmitted. It may be due to external factors such as atmospheric noise or due to internal factors such as shot noise from the hardware. An additive white Gaussian noise channel is used to model the effect of channel and receiver noise on the transmitted signal. The AWGN Channel block adds white Gaussian noise to a real or complex input signal. When the input signal is real, this block adds real Gaussian noise and produces a real output signal. When the input signal is complex, this block adds complex Gaussian noise and produces a complex output signal. This block inherits its sample time from the input signal. As seen from Figure 4.8 and 4.9, noisy channel increase the magnitude of the signal. AWGN channel is used because it represents a completely random process since any two samples in the noise process are uncorrelated and statically independent

Figure 4.8: Frequency spectrum AWGN off

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Figure 4.9: Frequency spectrum AWGN on

4.2 802.15.3 The cost or complexity of the device must be as minimal as possible for use in the personal area space. The PHY operates in the 2.4 – 2.4835 GHz frequency range. It specifies raw data rates of 11, 22, 33, 44 and 55M bit/sec; with the respective modulation type QPSK, DQPSK, 16-QAM, 32-QAM, and 64-QAM. The base rate of 22M bit /sec is uncoded while 11, 33, 44 and 55M bit/sec uses trellis coded modulation. Distance plays a role in transmission speed. The closer the device is to the access point, the higher the bandwidth. The highest rate, 55M bit/sec, is necessary for low-latency, multimedia connections and large-file transfers, while 11M bit/sec and 22M bit/sec rates are ideal for long-range connectivity for audio devices. Figure 4.10 shows a logical block diagram of a transceiver.

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Figure 4.10: Logical blocks in the transceiver PHY

4.2.1 Structure of the model The model consists of six main components. They are, the Bernoulli Binary Generator block, the DQPSK Modulator Baseband block, Transmitter/Receiver, the AWGN Channel block, the Free Space Path Loss block, DQPSK Demodulator Baseband block and the Error Rate Calculation block. The Bernoulli Binary Generator block generates random binary numbers using a Bernoulli distribution. The Bernoulli distribution with parameter p produces zero with probability p and one with probability 1-p. The Bernoulli distribution has mean value 1p and variance p (1-p). The Probability of a zero parameter specifies p, and can be any real number between zero and one. The DQPSK Modulator Baseband block modulates 37

digital data to analog format using the differential quaternary phase shift keying method. The

output

is

a

baseband

representation

of

the

modulated

signal.

The

Transmitter/Receiver shows the transition of the signal to and from the channel while the AWGN Channel block adds white Gaussian noise to a real or complex input signal. This block can process multichannel signals that are frame-based or sample-based. Variance of the noise like signal to noise ratio is simulate through this channel. The Free Space Path Loss block simulates the loss of signal power due to the distance between transmitter and receiver. The block reduces the amplitude of the input signal by an amount that is determined in either of two ways: By the Distance (km) and Frequency (MHz) parameters, if you specify Distance and Frequency in the Mode field By the Loss (dB) parameter, if you specify Decibels in the Mode field. The DQPSK Demodulator Baseband block demodulates a signal that was modulated using the differential quaternary phase shift keying method. The input is a baseband representation of the modulated signal. The Error Rate Calculation block compares input data from a transmitter with input data from a receiver. It calculates the error rate as a running statistic, by dividing the total number of unequal pairs of data elements by the total number of input data elements from one source. This block can be used to compute either symbol or bit error rate, because it does not consider the magnitude of the difference between input data elements. If the inputs are bits, then the block computes the bit error rate. If the inputs are symbols, then it computes the symbol error rate.

4.2.2 Free space path loss For any type of wireless communication, the signal disperses with distance. Therefore an antenna with a fixed area will receive less signal power the further it is from the

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transmitting antenna. Even with no other sources of attenuation or impairment are assumed, a transmitted signal attenuates over distance because the signal is being spread over a larger and larger area (Stallings 2004, p. 119). Figure 4.11 shows the losses against distance travelled.

180 170

f = 300 GHz

160

150

f = 30 GHz

140 f = 30 MHz Loss 130 (dB)

120 110

f = 300 MHz

100 90

f = 30 MHz

80 70 60 1

5

10 Distance (km)

50

100

Figure 4.11 Free space loss (Stallings 2004, p. 121) This form of attenuation is known as free space loss, which can be express in terms of the ration of the radiated power Pt to the power Pr receive by the antenna or in decibels, by taking 10 times the log of that ratio. For the ideal isotropic antenna free space loss is Pt / Pr = (4 π d) ² / λ = (4 π d)² / c² 39

where Pt = signal power at the transmitting antenna Pr = signal power at the receiving antenna λ = carrier wavelength d = progation distance between antennas c = speed of light (3x108 m/s)

4.2.3 Quadrature amplitude modulation QAM is a popular analog signalling technique that is used in the asymmetric digital subscriber line (ADSL) in some wireless standards. This modulation technique is a combination of ASK and PSK. QAM can also be considered as a logical extension of QPSK. QAM takes advantage of the fact that it is possible to send two different signals simultaneously on the same carrier frequency, by using two copies of the carrier frequency, one shifted by 90º with respect to the other. For QAM, each carrier is ASK modulated. The two independent signals are simultaneously transmitted over the same medium. At the receiver, the two signals are demodulated and the results combined to produce the original binary input (Stallings 2004, p. 151). d1(t) R/2 bps cos 2πfct

Binary input d (t) R bps 2 bit serial to parallel converter

~

carrier oscillator

-π/2

phase shift sin 2πfct

d2(t) R/2 bps 40

QAM output s (t) ∑

Figure 4.12: QAM modulator (Stallings 2004, p. 152) Figure 4.12 shows the QAM modulation scheme in general terms. The input is a stream of binary digits at a rate of R bps. The stream is converted into two separate stream bits of R/2 bps each, by taking alternate bits for the two streams. In the diagram, the upper stream is ASK modulated on a carrier of frequency fc by multiplying the bit stream by the carrier. Thus, a binary zero is represented by the absence of the carrier wave and a binary one is represented by the presence of the carrier wave at a constant amplitude. This same carrier wave is shifted by 90º and used for ASK modulation of the lower binary stream. The two modulated signal are then added together and transmitted. The transmitted signal can be express as follow: S(t) = d1(t) cos 2πfct + d2(t) sin 2π fct If two level ASK is used, then each of the two streams can be one of two states and the combined stream can be in on of 4 = 2 x 2 states. This is essentially QPSK. If four level ASK is used, then the combined stream can be in one of 16 = 4 x 4 states. Systems using 64 and even 256 states have been implemented. The greater the number of states, the higher the data rate that is possible within a given bandwidth. However, it also means that the greater the number of states, the higher the potential error rate due to noise and attenuation. Figure 4.13 uses the 16-QAM Modulator Baseband to modulate random data. Because the modulation technique is 16-QAM, the plot shows 16 clusters of points and there were no noise, the plot shows the 16 exact constellation points instead of clusters around the constellation points. The results are shown in Figure 4.14.

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Figure 4.13: 16-QAM ideal model

Figure 4.14: Ideal scatter diagram of 16-QAM

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The model in Figure 4.15 shows a random integer modulated using 16-QAM Modulator. After passing the data through a noisy channel, the model produces a scatter diagram of the noisy data. Figure 4.16 suggests what the underlying signal constellation looks like and shows that the noise distorts the modulated signal from the constellation. The SNR in the AWGN is set to 20 dB with an input signal of 1watt.

Figure 4.15: 16-QAM model with AWGN channel

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Figure 4.16: 16-QAM model with AWGN channel noise

4.2.4 Quadrature phase shift keying modulation The term quadrature implies that there are four possible phases (4-PSK) which the carrier can have at a given time. In QPSK, information is conveyed through phase variations. In each time period, the phase can change once. QPSK is a modulation scheme that transmits 2 bit information using four states of the phase (Shafi, Ogose & Hattori 2002, p. 221). Figure 4.17 shows a phasor diagram of the QPSK. The rate of change (baud) in this signal determines the signal bandwidth, but the throughput or bit rate for QPSK is twice the baud rate, thus effectively doubling the bandwidth of the carrier. The four phases are labelled {A, B, C, D} corresponding to the {0, 90, 180, 270} degrees (Tervo 1998).

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Figure 4.17 Phasor diagram of QPSK (Tervo 1998) Each of the four possible phase changes is assigned a specific two-bit value or dibit as shown in Table 4.1.

PHASE CHANGE (Degrees)

Example state change

Dibit

0

A to A

01

90

A to B

00

180

B to D

10

270

D to C

11

Table 4.1 QPSK phase state table (Tervo 1998) For example, a carrier shifting through the phase ADABAADCCA, the QPSK waveform will be as shown in Figure 4.18.

A

D

A

B

A

A

D

C

C

Figure 4.18 QPSK waveform (Tervo 1998)

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A

This signal has undergone the following phase transitions as shown in Table 4.2. PHASE A

D

A

B

A

A

D

C

C

A

...

Change - A-to-D D-to-A A-to-B B-to-A A-to-A A-to-D D-to-C C-to-C C-to-A ... Degrees Dibit

-

270

90

90

270

0

270

270

0

180

11

00

00

11

01

11

11

01

10

Table 4.2: Phase transitions (Tervo 1998) Therefore the transmitted information is 110000110111110110. Another option of QPSK modulation scheme is differential QPSK. DQPSK is a differential quadrature modulation technique that alternates between two quadrature symbol constellations which are offset by Pi/4 radians every other symbol period. A block diagram for the modulator is shown in Figure 4.19. In the modulator, a uniform random number generator produces symbols which are then differentially encoded and upsampled in order for the output to approximate a pulse train of delta functions. Gray encoding was used so that most symbol errors were 1 bit errors instead of 2 bit errors. The upsampled, differentially encoded, symbol stream is then pulse-shaped by a squareroot raised cosine filter with a rolloff factor of 0.35. The modulator output is left at baseband since the introduction of a carrier would only introduce spurious errors in the calculation of the Irreducible BER and since the Irreducible BER is determined by the multipath fading, the multipath delay spread, and the modulation technique irrespective of particular value of the carrier frequency.

46

Figure 4.19: Block diagram of DQPSK modulator (Anderson n.d.) Random data is generated using DQPSK modulator. The model in Figure 4.20 below plots the output of the DQPSK Modulator Baseband block with an offset of pi/4 shown in Figure 4.21.

Figure 4.20: DQPSK modulation

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Figure 4.21: Output of DQPSK modulator At the receiver, the signal passes through a matched filter, that is, a square-root raised cosine filter, is downsampled and the effects of the differential encoder are undone by the detection circuitry. Block diagram of a DQPSK demodulator is shown in Figure 4.22.

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Figure 4.22: Block diagram of demodulator (Anderson n.d.)

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5.0 CONCLUSION The objectives of this project have been achieved to a certain extent. A comparison between Bluetooth and 802.15.3 were analysed and discussed. The simulation in the previous chapter was carried out with the aim of testing the functionality of the transmission model. The accuracy of the results of the performance of the simulation model is dependent on how closely the simulation model resembles the actual system being modelled. The model is fully functional and produced close correct results. Different inputs were tested and the according output was produced. Based on this finding, a logical block diagram of the 802.15.3 transceiver had been made. Some characteristic of the 802.15.3 such as the modulation and AWGN channel were examined and presented. Implementing devices using IEEE 802.15.3 is clearly feasible. Compatibility and coexistence with other system especially those in similar market spaces, such as Bluetooth are also feasible. In addition, a better understanding and appreciation of the wireless technology was obtained through this research as well as through simulating them and studying their responses.

5.1 Recommendations Although the objectives of the project have been achieved to a certain extent, there are some areas that can be improved upon. One of the areas is to implement devices using the new 802.15.3 standard. Three targeted areas could benefit from short-range wireless connections. These include PC and peripheral devices, mobile devices and consumer electronics. Many devices in each of these three areas frequently communicate significant amounts of data over very short distances with other complementary devices, 50

usually by means of an interconnect cable. For example, a digital still camera, with a large storage capacity, typically requires a high-speed serial connection to the PC to transfer images. At the time of transfer, the distance between the PC and the camera is typically a few metres at most. Implementing devices using the IEEE 802.15.3 allows users to create a wireless link by enabling the necessary data rates in a radio suitable for cost-sensitive, battery-powered mobile devices, like a camera or PDA. Similar examples are smart phones, home entertainment centers, printers, handheld computers, camcorders, video projectors and MP3 players. By eliminating the need for a physical cable connection, a new level of user convenience and mobility is provided. Because 802.15.3 is being positioned as a high-speed wireless PAN, implementing this new standard, brings a step higher in the technology of WPAN. There is a need for this WPAN because it is designed to provide QoS for real time distribution of multimedia contents, like video and music as it is ideally suited for a home multimedia wireless network.

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6.0 REFERENCES Anderson, E.P., (n.d.), Determination of the irreducible BER for Pi/4-DQPSK. Retrieved: March 3, 2004, from http://www.stanford.edu/~eandersn/ee359/block.html#modulator. Barr, J.R. 2002, IEEE 802.15 TG3 and SG3a. Retrieved: January 10, 2004, from http://www.fcc.gov/oet/tac/april26-02-docs/FCC-TAC-802.15.3overviewNOPICT.ppt. Blankenbeckler, D., (n.d.), An introduction to bluetooth. Retrieved: March 10, 2004, from http://www.wirelessdevnet.com/channels/bluetooth/features/bluetooth.html. Cisco Systems 2003, CCNA1 network basic v3.0. Retrieved: February 24, 2004, from http://www.ece.curtin.edu.au/%7Ecisco/ccna/en_CCNA1_v30/start.html. Dornan, A. 2002, Standards spotlight: four standards out of the blue. Retrieved: January 10, 2004, from http://www.networkmagazine.com/shared/article/showArticle.jhtml?articleId=87033 64&pgno=3. Gilb, P.K. 2001, IEEE P802.15 working groups for wireless personal area networks (WPANs). Retrieved: April 24, 2004, from http://grouper.ieee.org/groups/802/19/pub/2002/Jan02/COEX-02004r0_TG3Coexistence-Capabilities.ppt. IEEE 2004, Bluetooth™ specification serves as foundation for IEEE 802.15 WPAN standard. Retrieved: April 23, 2004, from http://standards.ieee.org/announcements/bluespec.html. IEEE 802.15.1 2002, IEEE standard for information technology--telecommunications and information exchange between systems--local and metropolitan area networks-specific requirements part 15.1: wireless medium access control (MAC) and physical layer (PHY) specifications for wireless personal area networks (WPANs(TM)). Retrieved: January 24, 2004, from http://standards.ieee.org/catalog/olis/lanman.html. IEEE 802.15.3 2003. IEEE standard for information technology--telecommunications and information exchange between systems--local and metropolitan area networks-specific requirements part 15.3: wireless medium access control (MAC) and physical layer (PHY) Specifications for high rate wireless personal area networks (WPAN). Retrieved: September 21, 2003, from http://standards.ieee.org/catalog/olis/lanman.html. Khirat, S. & Kadhi, A. 2002. Wireless personal area network and home RF. Retrieved: August 23, 2003, from http://dessr2m.adm-eu.uvsq.fr/wpan.pdf.

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McGarrity, S. 2001, Bluetooth control logic design with stateflow. Retrieved: August 23, 2003, from http://www.mathworks.com/company/newsletters/digest/sept02/bluetooth.shtml. Nokia 2003, Bluetooth technology overview. Retrieved: March 3, 2004, from http://ncsp.forum.nokia.com/downloads/nokia/documents/Bluetooth_Technology_O verview_v1_0.pdf?ref=wdn. Pahlavan, K. & Levesque, A.H. 1995, Wireless information networks, John Wiley & Sons, New York. Shafi, M., Ogose, S. & Hattori, T. (ed), 2002, Wireless communications in the 21st century, IEEE Press, New Jersey. Stallings, W. 2004, Data and computer communications, 7th ed. Pearson Education, New Jersey. Sturman, C.F. 2003, Ubiquitous wireless communications. Retrieved: April 2, 2004, from http://www.same-conference.org/images/documents/tutorials/Tutorial_7.pdf. Tervo, R. 1998, EE4253 digital communications. Retrieved: February 12, 2004, from http://www.ee.unb.ca/tervo/ee4253/qpsk.htm. Tzamaloukas, M., (n.d.), An introduction to bluetooth architecture. Retrieved: April 4, 2004, from www.svcwireless.org/programs/seminar030301/ bluetooth_present-0303-2001.ppt. Walrand, J. & Varaiya, P. 2000, High-performance communication networks, 2nd ed. Academic Press, San Diego.

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