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Cross-Layer Design in Wireless Communications
Published in Jerry D. Gibson, Mobile Communications Handbook, 2017
Sayantan Choudhury, Jerry D. Gibson
Figure 32.6 shows the physical and MAC layer functional blocks and its interactions with the MAC scheduler [12]. Multiple Input Multiple Output (MIMO) transmission is an integral part of LTE design and can be used for transmit diversity, spatial multiplexing, beamforming, multiuser MIMO depending on the usage scenario. Additionally, there are 16 different modulation and coding schemes that are adapted based on the channel conditions. Furthermore, there is a Hybrid Automatic Repeat Request (HARQ) transmission mechanism that can provide fast retransmissions. In Reference 13, the authors investigated the optimal MIMO mode selection (spatial multiplexing or diversity) in order to maximize proportional fairness among users. The work was extended for multiuser MIMO transmission in Reference 14.
Performance analysis of LT code-based HARQ error control in underwater acoustic sensor networks
Published in Journal of Marine Engineering & Technology, 2022
P. Kaythry, R. Kishore, V. Nancy Priyanka
The ARQ technique totally works on retransmission of corrupted and lost packets based on the acknowledgement (ACK) received from the receiver or the time outs occur with respect to the sender (Lee and Cho 2011). Long propagation delay and error rate in UASN restricts the adoption of ARQ protocol, which introduces longer end-to-end delay, retransmission overheads and consumes more energy as well as bandwidth. Hybrid Automatic Repeat reQuest (HARQ) combines FEC for error detection and ARQ for retransmission of erroneous data in UASN. The sensed data in any UASN applications are sent from the source node to destination node over multiple hops. In this paper, the rateless code-based hop-by-hop HARQ scheme is proposed and investigated for reliable data transmission in UASN. The proposed method combines Recursive Luby transforms (LT) code, a simple rate less code-based FEC with hop-by-hop selective retransmission. The source node uses LT code to encode the original input packets into a set of ‘N’ encoded packets. Let ‘N’ be the sum of the number of redundant packets (m) and a number of input packets (n) i.e. ‘N=m+n’. To retrieve the ‘n’ original packets, the receiving node must receive ‘N’ encoded packets, which is greater than original packets ‘n’. During encoded packet transmission if more than ‘m’ packets are lost, the receiver discard the encoded packets and sends a feedback Negative Acknowledgement (NACK) packet and makes use of end-to-end ARQ retransmission technique.