In this paper, efficient turbo packet combining for single carrier (SC) broadband multiple-input--multiple-output (MIMO) hybrid--automatic repeat request (ARQ) transmission with unknown co-channel interference (CCI) is studied. We propose a new frequency domain soft minimum mean square error (MMSE)-based signal level combining technique where received signals and channel frequency responses (CFR)s corresponding to all retransmissions are used to decode the data packet. We provide a recursive implementation algorithm for the introduced scheme, and show that both its computational complexity and memory requirements are quite insensitive to the ARQ delay, i.e., maximum number of ARQ rounds. Furthermore, we analyze the asymptotic performance, and show that under a sum-rank condition on the CCI MIMO ARQ channel, the proposed packet combining scheme is not interference-limited. Simulation results are provided to demonstrate the gains offered by the proposed technique.
Deep Dive into Turbo Packet Combining for Broadband Space-Time BICM Hybrid-ARQ Systems with Co-Channel Interference.
In this paper, efficient turbo packet combining for single carrier (SC) broadband multiple-input–multiple-output (MIMO) hybrid–automatic repeat request (ARQ) transmission with unknown co-channel interference (CCI) is studied. We propose a new frequency domain soft minimum mean square error (MMSE)-based signal level combining technique where received signals and channel frequency responses (CFR)s corresponding to all retransmissions are used to decode the data packet. We provide a recursive implementation algorithm for the introduced scheme, and show that both its computational complexity and memory requirements are quite insensitive to the ARQ delay, i.e., maximum number of ARQ rounds. Furthermore, we analyze the asymptotic performance, and show that under a sum-rank condition on the CCI MIMO ARQ channel, the proposed packet combining scheme is not interference-limited. Simulation results are provided to demonstrate the gains offered by the proposed technique.
S PACE-TIME-BIT-INTERLEAVED coded modulation (ST-BICM) with iterative decoding is an attractive signaling scheme that offers high spectral efficiencies over multipleinput-multiple-output (MIMO)-intersymbol interference (ISI) channels [1], [2], [3], [4], [5]. To combat ISI in single carrier (SC) broadband ST-BICM transmission, frequency domain equalization, initially introduced for single antenna systems [6], [7], [8], [9], has been proposed using iterative (turbo) processing [10]. It is a receiver scheme that allows high ISI cancellation capability at an affordable complexity cost. In practical systems, unknown co-channel interference (CCI) caused by other transmitters (distant users and/or neighboring cells) who simultaneously use the same radio resource can dramatically degrade the link performance. This limitation can be overcome by using the so-called hybrid-automatic repeat
The Associate Editor coordinating the review of this paper and approving it for publication is Dr. M. C. Valenti. Manuscript received March 26, 2009; revised December 24, 2009;accepted T. Ait-Idir and H. Chafnaji are with the Communication Systems Department, INPT, Madinat Al-Irfane, Rabat, Morocco. They are also with Institut Telecom / Telecom Bretegne/LabSticc, Brest, France (email: aitidir@ieee.org).
S. Saoudi is with Institut Telecom / Telecom Bretegne/LabSticc, Brest, France. He is also with Université Européenne de Bretagne. request (ARQ) protocols, where channel coding is combined with ARQ [11], [12]. In hybrid-ARQ, erroneous data packets are kept in the receiver and used to detect/decode the retransmitted frame [13], [14], [15], [16], [17], [18], [19]. This technique is often referred to as “packet combining”. Practical packet combining schemes have been addressed in [20]. In [21], an elegant information-theoretic framework has been introduced to analyze the throughput and delay of hybrid-ARQ under random user behavior. Interestingly, the authors have shown that hybrid-ARQ systems are not interference limited, i.e., arbitrarily high throughput can be achieved by simply increasing the transmit power of all users even when multi-user detection (MUD) techniques are not used at the receiver. Motivated by the above considerations, we investigate efficient low-complexity turbo frequency domain reception techniques for SC broadband ST-BICM signaling with hybrid-ARQ operating over CCI-limited MIMO channels.
The powerful diversity-multiplexing tradeoff tool, initially introduced by Zheng and Tse for coherent delay-limited, i.e., quasi-static, MIMO channels [22], has been elegantly extended by El Gamal et al. to MIMO ARQ channels with flat fading, and referred to as diversity-multiplexing-delay tradeoff [23]. The authors have proved that the ARQ delay, i.e., maximum number of ARQ protocol rounds, improves the outage probability 1 performance for large classes of MIMO ARQ channels [23]. In particular, they have demonstrated that the diversity order can be increased due to ARQ even when the MIMO ARQ channel is long-term static, i.e., the MIMO channel is random but fixed for all ARQ rounds. The diversitymultiplexing-delay tradeoff has then been characterized in the case of block-fading MIMO ARQ channels, i.e., multiple fading blocks are allowed within the same ARQ round [25]. In [26], the outage probability of MIMO-ISI ARQ channels has been evaluated under the assumptions of short-term static channel dynamic 2 , and Chase-type ARQ [27], i.e., the data packet is entirely retransmitted. It has been shown that, as in the flat fading case, ARQ presents an important source of diversity, but its influence becomes only minimal when the ARQ delay is increased. This observation suggests that the design of practical packet combining schemes should target a high diversity order for early ARQ rounds. Supplementary retransmissions are then used to correct rare erroneous data packets, when they occur.
More recently, packet combining for MIMO ARQ systems has been investigated (e.g. [28], [29], [30], [31], [32], [33], [34], [35], [36]). Turbo combining techniques, where decoding is iteratively performed through the exchange of soft information between the soft-input-soft-output (SISO) packet combiner and the SISO decoder, have been proposed for the MIMO-ISI ARQ channel using unconditional minimum mean square error (MMSE)-aided combining [37], [26]. These approaches have then been extended to broadband MIMO code division multiple access (CDMA) systems with ARQ [38]. Time domain turbo packet combining for CCI-limited MIMO-ISI ARQ channels has been introduced in [39].
In this paper, we investigate efficient turbo receiver techniques for SC ST-BICM transmission with Chase-type ARQ over broadband MIMO channel with unknown CCI. We introduce a frequency domain MMSE-based turbo packet combining scheme, where all ARQ rounds are used to decode the data packet. By using an identical cyclic prefix (CP) word for multiple retransmissions of a symbol block, we p
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