Advanced Wireless Networks - 4G Technologies
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18 FUNDAMENTALS
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Receiver |
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SETUP |
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Intermediate node |
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SEARCH |
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BS |
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SEARCH |
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(Location |
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Sender |
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ACCEPT |
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SETUP |
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DIRECT |
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management) |
SETUP |
ACCEPT |
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ACK |
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Figure 1.13 Two-hop direct-transmission mode.
1.3.4.3 Handoff – two-hop direct-transmission mode to two-hop direct-transmission mode, one-hop direction-transmission mode or BS-oriented mode
If the destination or the intermediate node finds that the strength of the signal is less than a critical value, the handoff procedure is requested and executed at this time. The system will try to find another direct transmission path. If a direct transmission path is not found, the BS-oriented mode will take over. The handoff procedures are as follows:
(1)The destination or intermediate node sends the CHANGE message to the sender for changing connection.
(2)As the sender received the CHANGE request, it reinitiates the connection by sending out SEARCH. The next several steps are the same as in the initial connection setup.
1.3.4.4 How to solve the problem of BS failure
The method is also robust against BS failure in the middle of a connection. In Figure 1.14, when MH3 finds that its BS (BS2) failed, it performs the following steps until its BS is alive again (see Figure 1.15 for message flow).
(1)MH3 broadcasts the WHOSE-BS-ALIVE message to the neighbors.
(2)If one MH, say, MH2, receives the message and its BS is still alive, it records the sender ID and sends the BELONG message back to the sender.
HYBRID 4G WIRELESS NETWORK PROTOCOLS |
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MH6
BS3
MH5
MH4
BS2 |
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MH3 |
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MH2 |
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BS1
MH1
Figure 1.14 The BS failure problem.
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BS |
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Register |
ACK |
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MH2 (agent) |
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AGENT |
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ALIVE |
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WHOSE-BS- |
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BELONG |
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ACK |
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MH3
Figure 1.15 MH whose BS failed uses neighbor as an agent.
(3)MH3 receives the BELONG message and records MH2’s ID. Then it sends the AGENT message to MH2.
(4)After the agent (MH2) receives the AGENT message, it represents MH3 to register its location to its BS (BS1).
(5)MH2 will now relay the information to and from MH3. When MH2 or MH3 is leaving the other’s covering area, MH3 gives up the current agent and repeats steps 1–4 to find another agent. MH2 then removes the registration of MH3 from BS1.
20 FUNDAMENTALS
1.4 GREEN WIRELESS NETWORKS
4G wireless networks might be using a spatial notching (angle α) to completely suppress antenna radiation towards the user, as illustrated in Figures. 1.16 and 1.17. These solutions will be referred to as ‘green wireless networks’ for obvious reasons. In a mobile environment in the periods when the notch coincides with the direction of the base station (access point) the multihop protocol, as discussed in the previous section, can be used. In addition, to reduce the overall transmit power, a cooperative transmit diversity, discussed in Section 19.4, and adaptive MAC protocol, discussed in Appendix B (please go to www.wiley.com/go/glisic), can be used.
(a)
(b)
Figure 1.16 Three-dimensional amplitude patterns of a two-element uniform amplitude array for d = 2λ, directed towards (a) θ 0 = 0◦, (b) θ 0 = 60◦.
GREEN WIRELESS NETWORKS |
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Figure 1.17 Three-dimensional amplitude patterns of a 10-element uniform amplitude array for d = λ/4, directed towards (a) θ0 = 0◦, (b) θ0 = 30◦, (c) θ0 = 60◦,
(d) θ0 = 90◦.
22 FUNDAMENTALS
REFERENCES
[1]M. Mouly and M.-B. Pautet. The GSM System for Mobile Communications. Palaiseau: France, 1992.
[2]R. Kalden, I. Meirick and M. Meyer. Wireless internet access based on GPRS, IEEE Pers. Commun., vol. 7, no. 2, 2000, pp. 8–18.
[3]3rd Generation Partnership Project (3GPP), www.3gpp.org
[4]J. Khun-Jush, P. Schramm, G. Malmgren and J. Torsner. HiperLAN2: broadband wireless communications at 5 GHz. IEEE Commun. Mag., vol. 40, no. 6, 2002, pp. 130–137.
[5]U. Varshney. The status and future of 802.11-based WLANs, IEEE Comput., vol. 36, no. 6, 2003, pp. 102–105.
[6]Digital Video Broadcasting (DVB), www.dvb.org, January 2002.
[7]S. Glisic. Advanced Wireless Communications: 4G Technology. John Wiley & Sons: Chichester, 2004.
[8]J. Mitola III and G. Maguire Jr. Cognitive radio: making software radios more personal, IEEE Pers. Commun., vol. 6, no. 4, 1999, pp. 13–18.
[9]J. Border et al. Performance enhancing proxies intended to mitigate link-related degradations. RFC 3135, June 2001.
[10]D.C. Feldmeier, A,J. McAuley, J.M. Smith, D.S. Bakin, W.S. Marcus and T.M. Raleigh, Protocol boosters, IEEE JSAC, vol. 16, no. 3, 1998, pp. 437–444.
[11]M. Garc´ıa et al. An experimental study of Snoop TCP performance over the IEEE 802.11b WLAN. 5th Int. Symp. Wireless Personal Multimedia Commun., Honolulu, HI, Vol. III, October 2002, pp. 1068–1072.
[12]L. Munoz,˜ M. Garcia, J. Choque, R. Aguero and P. Mahonen, Optimizing internet flows over IEEE 802.11b wireless local area networks: a performance enhancing proxy based on forward error correction, IEEE Commun. Mag., vol. 39, no. 12, 2001, pp. 60–67.
[13]V. Jacobson. TCP/IP compression for low-speed serial links, RFC 1144, February 1990.
[14]Wireless LAN. IEEE Draft Standard P802.11, January 1996.
[15]Radio equipment and systems (RES); High performance radio local area network (HIPERLAN); Functional specification. ETSI, France, Draft prETS 300 652, 1995.
[16]D. Evans, Y. Du, C. Herrmann, S.N. Hulyalkar and P. May. Wireless ATM LAN with and without infrastructure. In 2nd IEEE Int. Workshop Broadband Switching Systems, Taipei, Taiwan, 1997, pp. 120–128.
[17]3GPP Technical Specification 25.401 UTRAN Overall Description.
[18]3GPP Technical Specification 25.410 UTRAN In Interface: General Aspects and Principles.
[19]3GPP Technical Specification 25.411 UTRAN Iu Interface: Layer 1.
[20]3GPP Technical Specification 25.412 UTRAN Iu Interface: Signalling Transport.
[21]3GPP Technical Specification 25.413 UTRAN Iu Interface: RANAP Signalling.
[22]3GPP Technical Specification 25.414 UTRAN Iu Interface: Data transport and Transport Signalling.
[23]3GPP Technical Specification 25.415 UTRAN Iu Interface: CN-RAN User Plane Protocol.
[24]3GPP Technical Specification 25.420 UTRAN Iur Interface: General Aspects and Principles.
[25]3GPP Technical Specification 25.421 UTRAN Iur Interface: Layer 1.
REFERENCES 23
[26]3GPP Technical Specification 25.422 UTRAN Iur Interface: Signalling Transport.
[27]3GPP Technical Specification 25.423 UTRAN Iur Interface: RNSAP Signalling.
[28]3GPP Technical Specification 25.424 UTRAN Iur Interface: Data Transport and Transport Signalling for CCH Data Streams.
[29]3GPP Technical Specification 25.425 UTRAN Iur Interface: User Plane Protocols for CCH Data Streams.
[30]3GPP Technical Specification 25.426 UTRAN Iur and Iub Interface Data Transport and Transport Signalling for DCH Data Streams.
[31]3GPP Technical Specification 25.427 UTRAN Iur and Iub Interface User Plane Protocols for DCI-1 Data Streams.
[32]3GPP Technical Specification 25.430 UTRAN Iub Interface: General Aspects and Principles.
[33]3GPP Technical Specification 25.431 UTRAN Iub Interface: Layer 1.
[34]3GPP Technical Specification 25.432 UTRAN Iub Interface: Signalling Transport.
[35]3GPP Technical Specification 25.433 UTRAN Iub Interface: NBAP Signalling.
[36]3GPP Technical Specification 25.434 UTRAN Iub Interface: Data Transport and Transport Signalling for CCH Data Streams.
[37]3GPP Technical Specification 25.435 UTRAN Iub Interface: User Plane Protocols for CCH Data Streams.
[38]3G TS 25.301 Radio Interface Protocol Architecture.
[39]3G TS 25.302 Services Provided by the Physical Layer.
[40]3G TS 25.303 UE Functions and Interlayer Procedures in Connected Mode.
[41]3G TS 25.304 UE Procedures in Idle Mode.
[42]3G TS 25.321 MAC Protocol Specification.
[43]3G TS 25.322 RLC Protocol Specification.
[44]3G TS 25.323 PDCP Protocol Specification.
[45]3G TS 25.324 Broadcast/Multicast Control Protocol (BMC) Specification.
[46]3G TS 25.331 RRC Protocol Specification.
[47]3G TS 24.008 Mobile Radio Interface Layer 3 Specification, Core Network Protocols – Stage 3.
[48]3G TS 33.102 3G Security; Security Architecture.
[49]GSM 04.18 Digital Cellural Telecommunications System (Phase 2+); Mobile Radio Interface Layer 3 Specification, Radio Resource Control Protocol.
[50]IETF RFC 2507 IP Header Compression.
[51]3G TS 25.305 Stage 2 Functional Specification of Location Services in UTRAN.
[52]3G TS 33.105 3G Security; Cryptographic Algorithm Requirements.
[53]G. Armitage and K. Adams. Packet reassembly during cell loss, IEEE Network, vol. 7, no. 5, 1995, pp. 26–34.
[54]U. Black. ATM Volume I: Foundation for Broadband Networks. Prentice-Hall: Upper Saddle River, NJ, 1992.
[55]M. Garrett. A service architecture for ATM: from applications to scheduling, IEEE Network, vol. 10, no. 3, 1996, pp. 6–14.
[56]D. McDysan and D. Spohn. ATM: Theory and Application. McGraw-Hill: New York, 1999.
[57]K. Sato, S. Ohta and I. Tokizawa. Broad-band ATM network architecture based on virtual paths, IEEE Trans. Commun., vol. 38, no. 8, 1990, pp. 1212–1222.
[58]T. Suzuki. ATM adaptation layer protocol, IEEE Commun. Maga., vol. 32, no. 4, 1994, 80–83.
2
Physical Layer and
Multiple Access
In this chapter we will briefly summarize the signal formats used in the existing wireless systems and point out possible ways of evolution towards the 4G system. The focus will be on ATDMA, WCDMA, OFDMA, MC CDMA and UWB signals [1–54].
2.1 ADVANCED TIME DIVISION MULTIPLE ACCESS-ATDMA
In a TDMA system each user is using a dedicated time slot within a TDMA frame as shown in Figure 2.1 for GSM or in Figure 2.2 for ADC (american digital cellular system). Additional data about the signal format and system capacity are given in Tables 2.1 and 2.2. The evolution of the ADC system resulted in the TIA (Telecommunications Industry Association) universal wireless communications (UWC) standard 136. The basic system parameters are summarized in Table 2.3. The evolution of GSM resulted in a system known as EDGE with parameters also summarized in Table 2.3.
If TDMA is chosen for 4G, the signal formats are further enhanced by using multidimensional trellis (space–time–frequency) coding and advanced signal processing [54]. This is also combined with Orthogonal frequency division multiplex (OFDM) and Multicarrier code division multiple access(MC CDMA) signal formats described below.
2.2 CODE DIVISION MULTIPLE ACCESS
Code division multiple access (CDMA) technique is based on spreading the spectra of the relatively narrow information signal Sn by a code c, generated by much higher clock (chip) rate. Different users are separated using different uncorrelared codes. As an example, the
Advanced Wireless Networks: 4G Technologies Savo G. Glisic
C 2006 John Wiley & Sons, Ltd.
26 |
PHYSICAL LAYER AND MULTIPLE ACCESS |
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Traffic |
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sacch |
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Traffic |
Idle / sacch |
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9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 |
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Multiframe |
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4.615 ms |
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TDMA frame |
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SF |
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SF |
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8.25 |
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Time slot |
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TRAINING |
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TB CODED DATA |
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SEQUENCE |
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CODED DATA |
TB |
GP |
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0.577 ms |
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Figure 2.1 Digital cellular TDMA systems: GSM slot and frame structure showing 130.25 bits/time slot (0.577 ms), eight time slots/TDMA frame (full rate) and 13 TDMA frames/multiframe (TB = tail bits, GP = guard period, SF = stealing flag).
One TDMA – frame (half rate)
Slot 1 |
Slot 2 |
Slot 3 |
Slot 4 |
Slot 5 |
Slot 6 |
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One slot |
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122 |
12 |
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G |
R |
DATA |
SYNC |
DATA |
SACCH |
CDVCC |
DATA |
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Slot format mobile station to base station |
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130 |
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RSVD |
SYNC |
SACCH |
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DATA |
CDVCC |
DATA |
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00..00 |
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Slot format base station to mobile station |
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Figure 2.2 ADC slot and frame structure for downand uplink with 324 bits/time slot (6.67 ms) and 3(6) time slots/TDMA frame for full-rate (half-rate) (G = guard time, R = ramp-up time, RSVD = reserved bits).
narrowband signal in this case can be a PSK signal of the form
Sn = b(t, Tm ) cos ωt |
(2.1) |
where 1/ Tm is the bit rate and b = ±1 is the information. The baseband equivalent of Equation (1.1) is
Snb = b(t, Tm ) |
(2.1a) |
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CODE DIVISION MULTIPLE ACCESS |
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Table 2.1 TDMA system parameters |
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Europe (ETSI) |
America (TIA) |
Japan (MPT) |
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Access method |
TDMA |
TDMA |
TDMA |
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Carrier spacing |
200 kHz |
30 kHz |
25 kHz |
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Users per carrier |
8 (16) |
3 (6) |
3 (tbd) |
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Modulation |
GMSK |
π/4 DPSK |
π/4 DPSK |
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Voice codec |
RPE 13 kb/s |
VSELP 8kb/s |
tbd |
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Voice frame |
20 ms |
20 ms |
20 ms |
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Channel code |
Convolutional |
Convolutional |
Convolutional |
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Codec bit rate |
22.8 kb/s |
13 kb/s |
11.2 kb/s |
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TDMA frame duration |
4.6 ms |
20 ms |
20 ms |
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Interleaving |
40ms |
27 ms |
27 ms |
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Associated control channel |
Extra slot |
In slot |
In slot |
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Handoff method |
MAHO |
MAHO |
MAHO |
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ETSI, European Telecommunications Standards Institute; MPT, Mobile portable terminal; TDMA, time division multiple access.
Table 2.2 Approximate capacity in Erlang per km2 assuming a cell radius of 1 km (site distance of 3 km) in all cases and three sectors per site. The Lee–Merit is number of channels per site assuming an optimal reuse plan
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GSM |
ADC |
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Analog |
pessimistic |
pessimistic |
pessimistic |
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FM |
optimistic |
optimistic |
optimistic |
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Bandwidth |
25 MHz |
25 MHz |
25 MHz |
25 MHz |
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Number of voice |
833 |
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1000 |
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2500 |
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3000 |
channels |
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Reuse plan |
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4 |
3 |
7 |
4 |
7 |
4 |
Channels/site |
119 |
250 |
333 |
357 |
625 |
429 |
750 |
Erlang/km2 |
11.9 |
27.7 |
40.0 |
41.0 |
74.8 |
50.0 |
90.8 |
Capacity gain |
1.0 |
2.3 |
3.4 |
3.5 |
6.3 |
4.2 |
7.6 |
(Lee–Merit gain) |
(1.0) |
(2.7) |
(3.4) |
(3.8) |
(6.0) |
(4.0) |
(7.2) |
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The spreading operation, presented symbolically by operator ε( ), is obtained if we multiply narrowband signal by a pseudo noise (PN) sequence (code) c(t, T c) = ±1. The bits of the sequence are called chips and the chip rate 1/T c 1/Tm . The wideband signal can be represented as
Sw = ε(Sn ) = cSn = c(t, Tc)b(t, Tm ) cos ωt |
(2.2) |
The baseband equivalent of Equation (2.2) is |
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Swb = c(t, Tc)b(t, Tm ) |
(2.2a) |