Exercise 3: Bluetooth BR/EDR

Transcription

1 Wireless Communicaions, M. Rupf. Exercise 3: Blueooh BR/EDR Problem 1: Blueooh Daa Raes. Consider he ACL packe 3-DH5 wih a maximum user payload of 1021 byes. a) Deermine he maximum achievable daa rae in he forward link R fwd and in he reverse link R rev for asymmeric communicaion and give he reasons for your soluion. b) Deermine he maximum achievable daa rae R sym for symmeric communicaion and give he reasons for your soluion. Consider a synchronous 64 kbps high qualiy voice connecion based on he SCO packe HV1 wih a maximum user payload of 10 byes. c) Deermine how frequenly HV1 packes have o be ransmied and how much capaciy is lef o ransmi ACL packes in he same communicaion direcion. Problem 2: Radio range. Assume ha a Blueooh device has an EIRP of 0 dbm and an Rx sensiiviy of -80 dbm (he specificaion requires -70 dbm a leas). Please deermine he maximum radio range d max beween wo such Blueooh devices wih he help of an exponen n=4 (indoor) model wih a breakpoin-disance of d 0 = 1m. Problem 3: Picone. Please answer he following quesions and give reasons for your answers. a) Please describe or characerize a Blueooh picone. b) Can a Blueooh device be a maser of more han one picone? c) Can a Blueooh device paricipae concurrenly in wo or more picones? d) Can wo Blueooh slaves direcly communicae wih each oher? 1/6

2 Wireless Communicaions, M. Rupf. Problem 4: Shor quesions. a) Which muliplex procedures does Blueooh use and for which purpose? b) How long is he Blueooh BR/EDR symbol period? And wha is he gross air bi rae for Blueooh BR and for Blueooh EDR, respecively? c) Which RF frequencies are used during he ransmission of a 3-slo packe? And which RF frequency is used in he firs slo afer he 3-slo packe? Assume ha he RF frequency f(k) is used in slo k where he ransmission of he 3-slo packe sars. d) In an EDR-packe here is a small guard ime. Why? e) How does adapive FH work and wha i is good for? f) Which procdures have o be made by he maser when connecing o slave wih an unknown Blueooh device address and how long does i ake? 2/6

3 Wireless Communicaions, M. Rupf. Problem 5: Packe ransmission. Consider a Blueooh picone wih a maser and 2 slaves and assume ha - here is a 64 kb/s SCO link beween Maser and Slave 1 based on packes, - here is an ACL link beween Maser and Slave 2 based on packes and - here are wo slos wih a (FH-) collision designaed wih a flash sign. In he following figure please complemen he packe ransmission. Moreover, please designae all HV1 packes wih figures 123 and all packes wih leers ABC such ha reransmissions (fas Auomaic Repea reques ARQ) are visible. Maser f(0) f(1) f(2) f(3) f(4) f(5) f(6) f(7) 1 Slave 1 Slave μs f(0) f(1) f(2) f(3) f(4) 3/6 f(5) f(6) f(7) 1 A C 3

4 Wireless Communicaions, M. Rupf. Soluion Problem 1 a) For asymmeric communicaion, 5 ime slos à 625 μs each are used o ransmi a 3-DH5 packe wih a maximum payload of 1021 Byes in he forward link and 1 ime slo à 625 μs is used in he reverse link (e.g. for an ACK, Time Division Duplexing TDD). R fwd = ( kb) / (6 625 μs) = kb/s In he reverse link, he maximum daa rae R rev is achieved if a 3-DH1 packe wih a maximum payload of 83 Byes is used. R rev = ( kb) / (6 625 μs) = kb/s b) For symmeric communicaion, 5 ime slos à 625 μs each are used o ransmi a 3-DH5 packe wih a maximum payload of 1021 Byes in he forward link and 5 ime slos are used o ransmi a 3-DH5 packe wih a maximum payload of 1021 Byes in he reverse link (Time Division Duplexing TDD). R sym = ( kb) / ( μs) = kb/s c) An HV1 packe can carry 1.25ms of speech/voice a a rae of 64 kb/s. Therefore, an HV1 packe mus be sen every wo ime slos. Hence, here is no more capaciy lef for he ransmission of ACL packes in he same communicaion direcion (because of he srong FEC used!). Problem 2 The indoor pah loss PL free = PL freespace (d 0 ) + 10 n log 10 (d max /d 0 ) = 80 db The freespace pah loss PL freespace (d 0 =1m) = log 10 (2.45) = 40 db => 10 4 log 10 (d max /1m) = 40 => d max = 10 m Problem 3 a) A Blueooh picone is an ad-hoc nework consising of 1 maser and 1 o 7 slaves whereby all devices of he picone have he same hopping sequence (and share he same 1 MHz channel). And he hopping sequence is derived from he maser s clock and he maser s Blueooh device address BD_ADDR. A number of independen picones may exis in close proximiy. Each picone has a differen physical channel (ha is a differen maser device and an independen iming and hopping sequence.) b) Core V4.0 sandard, Volume 1, Par A, Chaper 4.1.1: A Blueooh device can never be a maser of more han one picone. (Since in BR/EDR he picone is defined by synchronizaion o he maser s Blueooh clock i is impossible o be he maser of wo or more picones.) 4/6

5 Wireless Communicaions, M. Rupf. c) Core V4.0 sandard, Volume 1, Par A, Chaper 4.1.1: A Blueooh device may be a slave in many independen picones. I does his on a ime-division muliplexing basis. d) Two Blueooh slaves can communicae wih each oher only via he Blueooh maser. The Blueooh picone is a sar or poin-o-mulipoin-nework. Problem 4. a) FH-CDMA o separae picones and TDD o separae UL and DL. b) The Blueooh symbol period is 1 μs. The gross bi rae wih GFSK modulaion is 1 Mbps (BR) and wih π/4-dqpsk (EDR) and 8DPSK modulaion (EDR) 2 Mbps and 3 Mbps, respecively. c) The RF frequency shall remain fixed f(k) for he duraion of he packe. The RF frequency in he firs slo afer he 3-slo packe is he frequency f(k+3) d) The Enhanced Daa Rae (EDR) packes have a guard ime and synchronizaion sequence before he payload. This is a field used for physical layer change of modulaion scheme (GFSK for he packe header and 4- or 8-PSK for he payload). The packe header is GFSK-modulaed in order ha all Blueooh devices can decode i. e) Adaped picone physical channels can be used for conneced devices ha have adapive frequency hopping (AFH) enabled. There are wo disincions beween basic and adaped picone physical channels. The firs is he same channel mechanism ha makes he slave frequency he same as he preceding maser ransmission. The second aspec is ha he adaped picone physical channel may be based on less han he full 79 frequencies of he basic picone physical channel. AFH is used o improve resisance o radio frequency inerference by avoiding he use of crowded frequencies (e.g. used by WLANs) in he hopping sequence. f) The picone connecion procedure consiss of 1. he inquiry procedure and 2. he paging procedure if he Blueooh device address is unknown. The connecion procedure can las 5-10s. 5/6

6 Wireless Communicaions, M. Rupf. Problem 5 The packes are ransmied in he firs par of he ime slos. The maser sends always in even f(0) slos. f(1) f(2) f(3) f(4) f(5) f(6) f(7) Maser packes are periodically ransmied o guarany a ime bounded 64 kb/s voice service. packes are no reransmied (in conras o he esco packes EVx packes). Slave 1 The maser has o reransmi he -packe A because i is no acknowledged. The slave ges he -packe A wice correcly, bu can deec he replicaion because he SEQN-bi is equal in boh packe headers. Slave 2 1 The slave has o reransmi he -packe B because i receives a NAK in he header of he second -packe A. This procedure is also called fas Auomaic Repea 625 μs reques ARQ. Maser f(0) f(1) f(2) f(3) f(4) f(5) f(6) f(7) 1 A reransmission (fas ARQ) A 3 Slave Slave 2 B B 625 μs reransmission (fas ARQ) Please also see J. Schiller, Mobile Communicaions, Second Ediion, Addision-Wesley, 2003, chaper Physical links, figure /6