ITU-R REPORT M 2034-2003 Impact of radar detection requirements of dynamic frequency selection on 5 GHz wireless access system receivers《5千兆赫无线接入系统接收器动态频率选择的雷达探测要求的影响》.pdf
《ITU-R REPORT M 2034-2003 Impact of radar detection requirements of dynamic frequency selection on 5 GHz wireless access system receivers《5千兆赫无线接入系统接收器动态频率选择的雷达探测要求的影响》.pdf》由会员分享,可在线阅读,更多相关《ITU-R REPORT M 2034-2003 Impact of radar detection requirements of dynamic frequency selection on 5 GHz wireless access system receivers《5千兆赫无线接入系统接收器动态频率选择的雷达探测要求的影响》.pdf(7页珍藏版)》请在麦多课文档分享上搜索。
1、 Rep. ITU-R M.2034 1 REPORT ITU-R M.2034Impact of radar detection requirements of dynamic frequency selection on 5 GHz wireless access system receivers (2003) 1 Introduction Recommendation ITU-R M.1652 recommends that, in order to facilitate sharing with radars, mitigation techniques be implemented
2、by wireless access systems including radio local area networks (RLANs) (WAS) in the bands used by radars at 5 GHz. It describes a mitigation technique, named dynamic frequency selection (DFS), which requires a radar detection mechanism to be implemented. In addition, the Recommendation also gives th
3、e detection and response requirements with which the DFS should comply with. This Report considers how radars operating in the 5 GHz band can be detected by WAS without extreme constraints on the RF front-end design or on the system capacity of the WAS. Radar detection may only be possible during th
4、e time there is no active transmission in the WAS cell. During channel availability check time, there is no transmission for a significant time (e.g. 60 s). During in-service monitoring the detection can take place during moments of no uplink or downlink traffic. The detection of a radar pulse of po
5、wer above the so-called DFS threshold triggers a DFS procedure, and the access point must leave the channel within a short delay. In this Report the interplay of DFS threshold TDFS, WAS false alarm rate and radar detection failure rate by WAS are presented and discussed from the point of view of imp
6、lementation of radar detection in a WAS receiver. 2 Abbreviations and acronyms ACT: (channel) availability check time DF: detection failure probability DFS: dynamic frequency selection FA: false alarm probability OFDM: orthogonal frequency division multiplexing PDF: probability density function PRF:
7、 pulse repetition frequency RLAN: radio local area network RSS: received signal strength TDFS: DFS threshold WAS: wireless access system This Report was jointly prepared by Radiocommunication Study Groups 8 and 9, and any futher revision will also be undertaken jointly. 2 Rep. ITU-R M.2034 3 Assumpt
8、ions and methodology Radar detection by a WAS is characterized by two performance metrics: 3.1 Detection failure probability (DF) This is the probability that a radar is present in the channel but no radar pulse is detected by the WAS. DF must be as low as possible not to interfere with radars. A va
9、lue of DF = 1% is set as a target. The probability of detection varies with the power of the radar signal relative to the detector threshold setting in the receiver a higher power level increases the detection probability. 3.2 False alarm probability (FA) This is the probability that when a radar si
10、gnal is not present in the channel, interference pulses are detected by the WAS, triggering an unnecessary DFS procedure. This can happen when a noise or interference burst is mistaken for a radar pulse. Such a burst may be caused by WAS devices in the vicinity operating on the same channel or on th
11、e adjacent RF channels of the WAS system. A high interference/noise floor ratio in the WAS receiver will obviously increase the FA. However, this probability should be low as possible in order not to trigger unnecessary DFS procedures, which would severely limit the WAS capacity especially in dense
12、deployment scenarios. During channel availability check time, it is sufficient to be sure that the channel is not measured as occupied for some small percentage of the time. It will be seen that this percentage is a very sharp function of the WAS DFS threshold setting, with a few dB altering the FA
13、probability by many orders of magnitude. The WAS performs power measurements averaged over a duration rss_meas_duration, the measurements signal_rss being spaced by the averaging duration. Therefore, during channel availability check time (ACT), for example, the number of measurements performed is:
14、nb_trials = round (ACT / rss_meas_duration) The radar signal is received at a level of radar_ pulse_ power (dBm), (equivalent to TDFS in the notation of Recommendation ITU-R M.1652) and pulses have a duration of radar_ pulse_duration (ns). The radar signal bandwidth (MHz) is denoted by B. Many radar
15、s send pulses periodically, at a pulse repetition frequency (PRF) rate. For a rotating radar, the WAS will periodically receive a burst of pulses, such that the number of pulses occurring during the channel ACT, denoted by nb_RADAR_ pulses_ per_ACT will be greater than one. The 5 GHz orthogonal freq
16、uency division multiplexing (OFDM) RLANs sampling period used is T = 50 ns. 4 Detection criteria The detection criterion used here is based on absolute signal power measurements. If the measured power exceeds a certain threshold, then a radar is assumed to be detected. It is assumed that the signal
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