N.C. Ericsson, S. Falahati, A. Ahlen and A. Svensson, "Scheduling and adaptive transmission for the downlink in 4G systems," Future Telecommunication Conference Beijing, China, November 2001.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....user s data until the channel is good. This principle, which has been denoted multiuser diversity, represents a powerful tool for improving the system capacity. We have studied and developed schemes for using multiuser diversity by combining adaptive modulation and predictive scheduling [7, 16, 17, 20]. An important aspect of our work is that packets with different payloads should reliably be provided with different Quality of Service (delay and error probability) despite channel variations. 3.1 Link Adaptation and Scheduling We have so far primarily considered downlink (base to mobile) ....

....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 ....

N.C. Ericsson, S. Falahati, A. Ahlen and A. Svensson, "Scheduling and adaptive transmission for the downlink in 4G systems," Future Telecommunication Conference Beijing, China, November 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, ....

Ericsson N C, Falahati S, Ahln A, and Svensson A. Scheduling and adaptive transmission for the downlink in 4g systems. In Proceedings of Future Telecommunication Conference Beijing, Nov 2001.

....obtained from the inquiry process, the user scheduler will distribute time frames, and blocks of sub carriers within frames, among the users of each sector based on their current average SNR predictions. Here different degrees of sophistication can be used to achieve different transmission goals [8, 9, 10, 14], such as throughput and user satisfaction with delay and QoS constraints. Time [ms] Frequency [MHz] Frequency responce 20 40 60 80 100 120 140 3 2 1 0 1 2 3 Figure 2: From [6] Time frequency representation of an estimated channel obtained from real measurement data on a 5MHz ....

N. C. Ericsson, S. Falahati, A. Ahlen and A. Svensson, "Scheduling and adaptive transmission for the downlink in 4G systems," Proc. Future Telecommunication Conference, Beijing, China, November 2001.

....channel conditions. Regardless of the choice of criterion, which could be either maximization of system throughput or equalization to user satisfaction, the modulation format for the scheduled user is selected according to the predicted user signal to noise andinterference ratio (SNIR) see e.g. [6, 7, 8]. By using suf ficiently small time frequency bins the channel can be made approximately constant within the bins. We can thus use a flat fading AWGN channel assumption. Furthermore, since we have already determined the time slot allocation, via the inquiry process among adjacent cells described ....

N. C. Ericsson, S. Falahati, A. Ahlen and A. Svensson, "Scheduling and adaptive transmission for the downlink in 4G systems," Proc. Future Telecommunication Conference, Beijing, China, November 2001.

....channel conditions. Regardless of the choice of criterion, which could be either maximization of system throughput or equalization to user satisfaction, the modulation format for the scheduled user is selected according to the predicted user signal to noise andinterference ratio (SNIR) see e.g. [6, 7, 8]. By using suf ficiently small time frequency bins the channel can be made approximately constant within the bins. We can thus use a flat fading AWGN channel assumption. Furthermore, since we have already determined the time slot allocation, via the inquiry process among adjacent cells described ....

N. C. Ericsson, S. Falahati, A. Ahlen and A. Svensson, "Scheduling and adaptive transmission for the downlink in 4G systems," Proc. Future Telecommunication Conference, Beijing, China, November 2001.

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N.C. Ericsson, S. Falahati, A. Ahlen and A. Svensson, "Scheduling and adaptive transmission for the downlink in 4G systems," Future Telecommunication Conference Beijing, China, November 2001.

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