S. Falahati, N.C. Ericsson, A. Ahlen and A. Svensson, "Hybrid type-II ARQ/AMS and scheduling using channel prediction on fading channels," Nordic Radio Symposium 2001.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....info about the priorities, the size of the queues, and the required link service, some of which is also passed to the link layer (B) The scheduling decision (C) is updated by the link layer ARQ, and is then used to drain the queues, with a bit level resolution of the outflows. For details, see [7, 17, 19]. 3.2 Scheduling in Multiple Dimensions: An Adaptive OFDM System Proposal We have until now mainly studied adaptive modulation and scheduling in a TDMA time slot reservation framework. The whole slot is then assigned to one user, as will also mostly be the case in HSDPA for release 5 of WCDMA ....

....packets are first transmitted uncoded, with additional coding information transmitted later, if required due to an unsuccessful transmission. This combination attains high throughput, low delay and it makes the performance relatively insensitive to the unavoidable errors in channel predictions [16, 17, 19]. We use rate compatible convolutional codes, that enable soft decoding with acceptable computational complexity. We also study Turbo codes, of interest in particular in environments with high interference levels [9, 23, 24, 25] The critical issues of rate compatibility, channel estimation and ....

S. Falahati, N.C. Ericsson, A. Ahlen and A. Svensson, "Hybrid type-II ARQ/AMS and scheduling using channel prediction on fading channels," Nordic Radio Symposium 2001.

....to transmission rates of 1, 1=2, 1=3, and so on, since each re transmission does not provide Go back n ARQ systems usually result in more frames than the erroneous one being re transmitted. any new information, it only repeats what was previously sent. This is avoided in a hybrid ARQ system [14, 23, 25, 26]. To start with, the data stream is encoded using a low rate convolutional code, that, through tailbiting or zero tail [22] results in a block wise encoded stream. Then, each block is punctured to several versions of increasingly higher rates, each version being a subset of the one with the ....

....it is to make a correct and accurate prediction of the channel quality. So, in a real system, a trade o between prediction horizon and scheduling gain, has to be made. The performance for some di erent link layer strategies, with unreliable channel predictions, are evaluated in Chapter 7 and in [19, 23]. 6.1.3 Motivation 3: Ful lling Quality of Service Guarantees Another issue for future data communication over wireless links, is quality of service (QoS) Although there is no agreed upon de nition of what QoS really is, it most certainly is better met by increased throughput, reduced error ....

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S. Falahati and N. C. Ericsson. Hybrid type-II ARQ/AMS and Scheduling using Channel Prediction for Downlink Packet Transmission on Fading Channels. In Proc. PCC Workshop, Nynashamn, Sweden, Apr. 2001.

....provides the error correcting codes with manageable data, avoiding bandwidth consuming re transmissions. The main drawback is the sensitivity to channel prediction errors. An even more promising solution, according to preliminary investigations, would be a combination of the two methods [8]. The combined method successfully reduces the drawbacks of the individual methods described above: Knowledge of the channel conditions indicates the initial coding rate modulation to use, reducing the delay due to numerous NAKs. The presence of the ARQ scheme provides robustness against ....

S. Falahati and N. C. Ericsson. Hybrid type-II ARQ/AMS and Scheduling using Channel Prediction for Downlink Packet Transmission on Fading Channels. In Proc. PCC Workshop, Nynashamn, Sweden, Apr. 2001.

....to try to take advantage of combining this very variability with the different flow requirements. A popular approach is to adapt transmission parameters to the state of the channel depending on the QoS requirements of the flow. Some approaches study adaptive modulation, coding and power control [2, 3, 5, 6, 7, 8], others concentrate on channel aware (or state dependent) scheduling [1, 4, 5, 9, 12, 12, 13, 14, 17] trying to use the bad channel times (where any transmission would be lost) of one wireless terminals (WT) to send data to another one which is experiencing a good channel at the same time or, ....

Falahati S, Ericsson N C, Ahln A, and Svensson A. Hybrid type-ii arq/ams and scheduling using channel prediction on fading channels. In Nordic Radio Symposium 2001.

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S. Falahati, N.C. Ericsson, A. Ahlen and A. Svensson, "Hybrid type-II ARQ/AMS and scheduling using channel prediction on fading channels," Nordic Radio Symposium 2001.

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