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Dynamic Frequency Sharing, wireless multi-station downstream transmission

posted Apr 17, 2015, 6:21 AM by Rute Sofia   [ updated Apr 17, 2015, 6:23 AM ]

DFS is a software-based mechanism that targets short-range wireless networks where transmission is based on a shared medium (e.g. broadcast) and which rely on OFDM for data transmission. DFS is applicable downstream, from the antenna to the station, and relies on techniques both from OSI Layer 1 and 2 to assist data transmission to multiple stations within a time-frame that based only in OFDM could only serve the purpose of serving a single station.

Allowing downstream transmission via one symbol to multiple stations provides the means to improve the performance of current solutions three-fold. Firstly, by allowing data to be transmitted on the same time-frame to multiple stations, the control overhead is reduced in comparison to the current standards, as the same control information is used to transmit data to multiple stations. Secondly, for real-time traffic there is an upper bound on usable data rates. For instance, for Voice over IP (VoIP) traffic it is approximately 486 kilobits per second (kbps), and for video traffic such limit is of 1 megabit per second (Mbps). Due to this limit, increasing the capacity of the wireless link does not suffice to improve performance as buffering cannot be used in real-time traffic. With the increasing popularity of VoIP, online-gaming, this inefficiency becomes an important problem to be solved. By multiplexing data downstream (from controller to stations) to several stations our solution is expected to provide a better usage of high data rate channels, which is a beneficial aspect in terms of real-time traffic. Thirdly, instead of transmitting to stations one by one, thus wasting time in particular if the first station that captures the medium is what is known as „slow“ station (e.g. away from the antenna or attaining severe interference around), our solution provides a way to transmit „simultaneously“ data to several stations within the same time frame thus decreasing the round-trip time and the latency of the transmission.


DFS has been conceived, validated, and implemented by COPELABS (Rute Sofia and Luis LOpes) and University of Kent (Huseyin Haci, Hassan Osman, Huiling Zhu) in the context of the European project ULOOP - User-centric Wireless Local Loop.

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