Adaptive Frequency Hopping Technique Research Articles

BuSAR: Bluetooth Slot Availability Randomization for Better Coexistence With Dense Wi-Fi Networks

The last decade has witnessed the ever-increasing deployment of Wi-Fi networks and the explosion of Bluetooth-based applications. As a result, the coexistence of Bluetooth piconets with highly-dense Wi-Fi networks is a common phenomenon currently. Unlike Wi-Fi that conducts carrier sensing before channel access, Bluetooth adopts frequency hopping based on a predefined hop sequence, which inevitably incurs considerable cross-technology interference to Wi-Fi. While the Adaptive Frequency Hopping technique is standardized for interference reduction, it does not perform well in current practice where densely-deployed Wi-Fi networks commonly cover the whole 2.4 GHz unlicensed spectrum. In this context, this article presents BuSAR, a novel approach to account for the coexistence problem between Bluetooth piconets and dense Wi-Fi networks. BuSAR embodies the first work to aim at mitigating the cross-technology interference between Bluetooth and highly-dense Wi-Fi networks in a distributed manner. At the heart of BuSAR lies a subtle technique called B l u etooth s lot a vailability r andomization, which exploits the redundancy of erroneous Bluetooth packets for better Bluetooth/Wi-Fi coexistence. With BuSAR adopted, multiple Bluetooth piconets are guaranteed to operate independently and only a lightweight algorithm is needed to be implemented at each Bluetooth device. Both theoretical analysis and experimental results validate the feasibility and superiority of BuSAR.

An Adaptive FH/MC-CDMA to Improve Channel Quality for Multiuser Using Variable Code-Based Carriers

The adaptive variable code-based carriers for multiusers in a common channel of communication is a technique of Multi-Carrier Code Division Multiple Access (MC-CDMA). It is an advanced mode of communication, where multiple users are communicating with different code and a different carrier. The proposed adaptive frequency hopping technique in MC-CDMA will give high signal to noise ratio value mitigating multiple access interference. Proposed adaptive technique detects multi-users with the help of matched filters. The simulation of the above system is done with correlated sub-carriers in the presence of realistic fading channels and even imperfect channel state information for recovering at the transmitter. The performance of an improved allocation algorithm for MC-CDMA system with adaptive frequency hopping is investigated. Imperfect channel state information at the base station does not affect the performance of the proposed technique due to the combined allocation algorithm and multi-user detector employment. The above combination mitigates multiple access interference efficiently, and increases the system capacity in a significant way compared to non-adaptive variable code-based carrier system. The results of the simulation confirm the above said performance factors with realistic correlated sub carriers that are faded with practical communication system parameters.