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In this paper, we discuss the problem of non-collocated coexistence of WiFi and 4G technologies such as WiMAX and LTE due to adjacent channel interference. The existing literature has many solutions and schemes to address the problem of shared channel coexistence and adjacent channel coexistence on multi-radio platforms. Results for Non-collocated coexistence in adjacent channels in wireless remain very scattered and few. Radio devices operating on Broadband Wireless Access (BWA) 4G wireless technologies like IEEE 802.16 (WiMAX) and LTE-A require very low noise floor. BWA spectrum allocations in 2.3 GHz and 2.5GHz have resulted in these networks to be very close to 2.4 GHz ISM band used by WiFi. We show, with measurements on our test-bed and from existing results, that the low-cost filters on WiFi devices are not very effective in controlling the out-of-band emissions to satisfy the low noise floor requirements of 4G. We propose schemes to mitigate the problem of adjacent channel interference by a time sharing mechanism across technologies by protecting packet receptions on both IEEE 802.11 and the IEEE 802.16 side. We demonstrate the effectiveness of our scheme to protect WiMAX packets by ensuring a controlled silence zone in the WiFi network using a test-bed. We also show that there is very limited adverse impact, due to the use of our scheme, on the system throughput of the non-collocated WiFi network operating in the adjacent channel.
Date of Conference: 22-25 Oct. 2012