Wireless Future - Telenor

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Figure 2 The Bluetooth protocol stack 66 Data Applications TCP/IP HID RFCOMM Audio L2CAP Link Manager Baseband RF Control 2.1 Overview Bluetooth is a radio technology to connect devices, without using wires, at a relatively short distance. The most common mode allows units to communicate within a distance of 10 m from each other. A high power mode is also defined for which the expected distance in free line of sight is 100 m. The radio works in the globally available 2.4 GHz Industrial, Scientific, and Medical (ISM) band. Bluetooth devices connect in a star topology where the central unit is denoted master and the devices connected to this are denoted slaves. The master controls all traffic in the network. Both synchronous (voice) and asynchronous traffic (data) is supported. The data can be symmetric or asymmetric. The available user data rate is up to 433 + 433 kb/s (symmetric) and 723 + 57 kb/s (asymmetric), assuming no retransmissions are needed. 2.2 Radio Bluetooth operates in an unlicensed band which is free for use all over the world. This ensures that Bluetooth equipped devices can be brought along and used when travelling abroad. Due to the unknown state of noise and interference in the band, it was not possible to design the Bluetooth radio interface for a known interference situation (in contrast to cellular systems such as GSM and UMTS, where the band is licensed and interference to a certain extent can be controlled). For instance, the IEEE 802.11 WLAN (and its derivatives) operates in the same band, and domestic microwave ovens heating food may leak a substantial amount of electromagnetic radiation here as well. The Bluetooth air interface has been specifically designed to accommodate for varying interference characteristics by incorporating frequency hopping (FH) spread spectrum techniques. In the used ISM band there are 79 channels defined, each being 1 MHz wide. During communication, the devices spread with 1600 hops/s covering all channels according to a pseudo-random sequence. Binary GFSK modulation is used with a signalling rate of 1 Msymbols/s, which gives the radio signal an instantaneous –20 dB bandwidth of 1 MHz. The allowable output power in the 2.4 GHz ISM band is restricted by different regulatory bodies in different countries. For Bluetooth transmission, the applicable paragraphs in ETSI 300 328 and FCC part 15 must be considered. Three different power classes (denoted class 1, 2, and 3 devices) have been defined for Bluetooth radio transmitters. They correspond to 100 mW (20 dBm), 2.5 mW (4 dBm), and 1 mW (0 dBm) output power, respectively. A power control functionality is required for class 1 Bluetooth devices transmitting over 0 dBm. This is to prevent unnecessary interference to other radio transceivers operating in the neighbourhood and in this ISM band. In the design of the radio interface, much effort has been made to facilitate simple (low-cost) ASIC implementations of the radio hardware with none or only a few external components. For instance, the relaxed requirements on the noise figure (23 dB) allows a margin for substrate noise so that a low-current LNA can be used. The transmit/receive turn-around time (220 ms) is large enough to support a single synthesiser solution. The phase noise requirement (–89 dBc/ Hz at 500 kHz) is easy enough to allow for an integrated VCO. On the other hand, the requirements on the adjacent channel interference suppression are rather strict to ensure that system performance is satisfactory also in quite severely interfered environments. For further details on implementation issues, see [2]. In principle, the radio functionality is controlled by a state machine which usually is denoted baseband (or link) controller. The behaviour of the state machine is controlled by the link manager (described in Figure 3), which in its turn is controlled by the application running on the host. 2.3 Baseband Bluetooth uses time division duplex (TDD) communication. The time axis is divided into 625 ms long slots. For each slot, a different hop carrier is used, resulting in a nominal hop rate of 1600 hops/s. The master starts transmissions in even slots, while a slave can only start transmitting in odd slots. A Bluetooth master unit and all slaves connected to it constitute a piconet. Only master/slave traffic is possible. For slave/slave traffic, either the master has to act as a relay be- Telektronikk 1.2001
tween the slaves, or the slaves set up a piconet of their own (in which one of the slaves now becomes the master). The master decides which slave gets access to the piconet channel by addressing it. After having received something from the master, the addressed slave can return information in the following time slot. To give a slave a possibility to initiate communication, the master must poll the slave periodically with a maximal interval that was agreed upon when the slave joined the piconet. When several piconets exist simultaneously in range of each other, they constitute a scatternet. From a system point of view, the aggregate throughput is increased by creating many piconets that occasionally interfere with each other, rather than having one or a few large piconets where interference between piconets is non-existent or very small. A unit (slave or master) can participate in more than one piconet at a time by utilising time sharing between the different piconets (note that by definition, a unit can only be master in one of the piconet(s) it belongs to). The process of sharing time between piconets is referred to as interpiconet scheduling. Similarly, interpiconet communication occurs when information flows between two piconets. Three sample topologies are depicted in Figure 4. Each Bluetooth device obtains a unique, factory pre-set, 48 bit address, denoted BD_ADDR. This address is used when setting up a connection to a device. This procedure is denoted paging. If, however, a device does not know which other units are in range, it must find out this first through the inquiry procedure. Bluetooth devices that receive an inquiry message respond with their BD_ADDR and some timing information. Using this information, the inquirer can then page an arbitrary device that has responded. When the connection is made, the piconet master will give the slave a three bit active member address, AM_ADDR, that is used for subsequent addressing within the piconet. The three address bits restrict the number of active slaves to seven, since the all-zero AM_ADDR is reserved for broadcast messages. Slave A Master B Telektronikk 1.2001 Slave A Master B a) b) Slave C 2.4 GHz Bluetooth Radio Host Link Manager and I/O A Bluetooth packet consists of a 72 bit access code, a 54 bit packet header, followed by the payload data. The access code serves two purposes: it is used to fine-tune the receiver in order to remove DC-offset, and the receiver can time synchronise to align time slots with the transmitter. These operations are necessary due to relative drift between the crystals in the involved units. The packet header contains information about the recipient and what packet type the payload is. Information used by the ARQ protocol is also included there. In the Bluetooth standard, different packet types have been defined. Packets that are typically used for data traffic contain cyclic redundancy check (CRC) bits to check the payload for errors. The payload length is typically 240 bits. If conditions are favourable (i.e. when the number of bit errors due to noise is relatively small) longer packets can be used with a payload length up to 2745 bits. The short packets can be sent within one time slot. Longer packets can occupy several (up to 5) time slots. Since the frequency is not changed during the transmission of a packet, the effective hop rate decreases when long packets are used. Packets typically used for Slave A Master B c) Slave C Slave Y Master X Baseband Link Controller Figure 3 Functional blocks in the Bluetooth system Figure 4 Different topologies for Bluetooth piconets; a) single slave operation, b) multi-slave operation, and c) scatternet with interpiconet communication 67
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Telektronikk Volume 97 No. 1 - 2001
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Per Hjalmar Lehne (42) obtained his
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Stein Svaet (41) is Senior Research
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Pbit/day 6 150 125 100 75 50 25 0 F
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8 Video communication as a utility
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10 The idea of reconfigurable mobil
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12 Switched lobe Dynamically phased
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Figure 10 The All IP vision Figure
Page 18 and 19: 16 The IP world has some problems t
Page 20 and 21: 18 Abbreviations and acronyms less
Page 22 and 23: Jorge Pereira (40) obtained his Eng
Page 24 and 25: (Millions) Figure 1 Exponential gro
Page 26 and 27: 24 Defining Generation based upon D
Page 28 and 29: Multi-mode Terminal by Software Rad
Page 30 and 31: distribution layer possible return
Page 32 and 33: 30 A Co-Ordinated Approach to 4G As
Page 34 and 35: Figure 2 Applications will grow fas
Page 36 and 37: Figure 5 Evolution from multi-mode
Page 38 and 39: Operator/Provider download librarie
Page 40 and 41: Radio network subsystem - service c
Page 42 and 43: Dr. Techn. Jørgen Bach Andersen (6
Page 44 and 45: Figure 3 Two arrays with M and N el
Page 46 and 47: Figure 5 Cumulative probability dis
Page 48 and 49: Figure 8 As in Figure 5, but with F
Page 50 and 51: 48 Conclusion The challenge of prov
Page 52 and 53: 50 models are described simply by a
Page 54 and 55: 52 ping intervals or “quantizatio
Page 56 and 57: Figure 3 ASE as a function of the a
Page 58 and 59: 56 7 Conclusion and Further Researc
Page 60 and 61: Dave Wisely (39) graduated in 1982
Page 62 and 63: Figure 2 Business case study Figure
Page 64 and 65: Figure 6 BRAIN QoS architecture 62
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Page 70 and 71: Figure 5 A Bluetooth radio module i
Page 72 and 73: 70 • Instant postcard: A Bluetoot
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Page 76 and 77: Table 1 Allocated HiperLAN bands (i
Page 78 and 79: Figure 4 Basic MAC frame structure
Page 80 and 81: 78 Preamble BCH FCH ACHs Preamble S
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Page 84 and 85: 82 5 References 1 CEPT. ERC Decisio
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Page 106 and 107: Figure 4 OSA architecture service c
Page 108 and 109: Do van Thanh (43) obtained his MSc
Page 110 and 111: Figure 2 The first use case diagram
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Page 116 and 117: Figure 10 Initiating call from PSTN
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Figure 13 Splitting the incoming st
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Figure 17 A set of communication de
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120 Box 3 continued Session Descrip
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Figure 21 A laptop and peripheral d
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124 Box 4 - Bluetooth Bluetooth is
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126 6 The ICEBERG project. (2001, M
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128 new door towards the upcoming f
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? Figure 1 The Mobile Service Platf
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Figure 2 Needs and Related Services
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134 Telektronikk 1.2001
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136 Telektronikk 1.2001
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Anne Lise Lillebø (52) is Adviser
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140 with other SDOs (Standards Deve
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142 Box 2 - ETNO Declaration We, th
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Arve Meisinset (52) is Senior Resea
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146 In ITU-T we have seen needs to
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148 Each viewpoint constitutes a se
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Figure 2 UML class diagrams for tra
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152 The functionality describing th
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154 9 Potter, B et al. An introduct
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