hsdpa技術(shù)簡(jiǎn)介和分析(編輯修改稿)
2025-06-15 16:08 本頁(yè)面
【文章內(nèi)容簡(jiǎn)介】 itted ? A sequence number is required to identify the block ? The greater the feedback delay the larger the maximum sequence number must be. SR (2/2) Two difficulties ? UE memory requirements are high – the mobile needs to store soft samples for each partially received block. ? Requires the receiver to reliably determine the sequence number of each transmission. SAW HARQ (1/4) ? Characteristic – Stopandwait is one of the simplest forms of ARQ . In stopandwait, the transmitter operates on the current block until the block has been received successfully. – stopandwait protocol amp。 Hybrid ARQ protocol SAW HARQ (2/4) ? Advantage – require very little overhead 。 – control overhead is minimal 。 – Acknowledgement overhead is minimal 。 – memory requirements at the UE are minimized 。 SAW HARQ (3/4) ? major drawback acknowledgements are not instantaneous and therefore after every transmission, the transmitter must wait to receive the acknowledgement prior to transmitting the next block. the channel remains idle and system capacity goes wasted. SAW HARQ (4/4) Robustess 1 2 3 4 5 6 7 8 9 101 2C A C KS N 13 4 5 6 7 8C A C KS N 2C A C KS N 3C A C KS N 4D a t a b l o c k 2 i s n o tr e t r a n smi t t e d d u e t o t h er e c e i v e d C A C K 3N channel SAW HARQ ? no system capacity goes wasted ? the receiver has to store N blocks Timing relations for 2channel HARQ process HSPDSCH a t Nod e BHS DP A TTIUL fe e d b a c k a t UEUL fe e d b a c k a t Nod e BHSPDSCH a t UEUE c h a n n e l 1AC K/ NAC KUE c h a n n e l 1AC K/ NAC KUE c h a n n e l 2 UE c h a n n e l 2 UE c h a n n e l 1UE c h a n n e l 1 UE c h a n n e l 1 UE c h a n n e l 1TU EPTN BPT pr opT pr opTA CKChase Combining ? The simplest form of Hybrid ARQ scheme was proposed by Chase, also called HARQtypeIII with one redundancy version. ? The basic idea in Chase’s bining scheme is to send a number of repeats of each coded data packet and allowing the decoder to bine multiple received copies of the coded packet weighted by the SNR prior to decoding. Combining Schemes Combining Schemes The second is the best. RCPT codes in HARQ Complexity Evaluation (1/2) ? Processing time – The time required for processing the tasks depends on the number of timeslots in the HSDPA TTI (number of bits to be processed). – The shorter the HSDPA TTI the less time there is available
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