Ayham Z. Al-Banna

Spectral signatures and interference of 802.11 Wi-Fi signals with Barker code spreading

This paper characterizes interference in 802.11 Wireless Fidelity (Wi-Fi) systems that utilize Barker codes as spreading sequences. Particularly, detailed spectral analyses are performed. These studies result in exact power spectral densities (PSDs) for 1 Mbps and 2 Mbps signaling schemes that define their spectral signatures. Investigation of the leakage of interference power into adjacent 802.11 channels, which can be useful for the deployment of cognitive radios, is presented The theoretical and computer simulation results for the Wi-Fi signal PSDs are verified through experimental measurements and emulation

Characterization of an Unintentional Wi-Fi Interference Device - the Residential Microwave Oven

Some devices not used for data communications radiate in the 2.4 GHz wireless-fidelity (Wi-Fi) band, thus causing unintentional interference that degrades the performance of IEEE 802.11 wireless systems. An analytical model for radio emissions from one of the most common unintentional interferers, the residential microwave oven, is developed from laboratory measurements. Simulation of the analytical model results in a power spectral density and spectrogram that are in good agreement with experimental data. An interference mitigation technique is proposed for the microwave oven emission

11 Mbps CCK - Modulated 802.11b Wi-Fi: Spectral Signature and Interference

The spectral signature of IEEE 802.11b 11 Mbps complementary code keying (CCK) wireless fidelity (Wi-Fi) signals is identified through an exact derivation of its power spectral density (PSD). This theoretical result was verified by computer simulation. The spectral signature of the 11 Mbps CCK-spread signal is compared with that of the 5.5 Mbps CCK-spread signal, as well as the Barker-spread signals. The adjacent channel interference power and interference temperature caused by different Wi-Fi interferers are calculated and presented

Interference Mitigation in IEEE 802.11G OFDM Systems with Smart Antennas and Tapped Delay Lines

In an 802.11 wireless environment, signals that use orthogonal frequency division multiplexing (OFDM) and OFDM with cyclic prefix code (OFDM-CPC) present interference to other wireless users. This work thoroughly analyzes the interference these signals cause and contrasts the results to that of narrow band interferers. Smart antennas with tapped-delay-lines are used to mitigate the interference effect from these signals. The optimal values for the delay lines parameters (number of taps and amount of delay provided by each delay unit) to restore the performance at minimum cost are found

Adaptive Antennas for Interference Mitigation of Barker/CCK Spread Wi-Fi Signals

A study of interference caused by adjacent IEEE 802.11 Barker-code spread and complementary code keying spread wireless fidelity signals used in wireless local area networks is presented. The interference resulted from these signals is thoroughly analyzed and compared to that caused by bandlimited flat spectral interferers as well as narrow band interferers. Adaptive antennas employing tapped-delay-lines are used to mitigate the interference effect from these signals. The optimal values for the delay-line parameters to restore the performance at minimum cost are found

Optimal design layout of a tactical GSM communication system with nonuniform traffic

An algorithm suitable for tactical TDMA-GSM communication system design is developed. The algorithm computes the minimum number of base stations for a given geography and provides for maximum coverage in the presence of nonuniform offered traffic. Optimal antenna location and sectorization are used to achieve the target coverage. The algorithm produces two distinct cell shapes (hexagonal and square) as the topography and propagation environment are changed. The cell size adapts to the traffic pattern to ensure the required quality of service, specifically a maximum blocking probability. As compared to other published work, this layout algorithm provides a comprehensive approach that takes into account both the nonuniform offered traffic and the areas varied topography. Several realistic system specifications were considered to simulate the minimum cost system resulting in a 20% savings in the required number of base stations compared to traditional design methods

Multi-Element Adaptive Arrays with Tapped Delay Lines for Interference Mitigation in IEEE 802.11G OFDM Systems

In the unlicensed ISM wireless band, signals that use Orthogonal Frequency Division Multiplexing (OFDM) and OFDM with Cyclic Prefix Code (OFDM-CPC) present interference to other wireless users. We analyze the interference these broadband signals cause and contrast the results to that of narrowband interferers. Multi-element adaptive antennas with tapped-delay-lines are used to mitigate multiple interferers. It is shown that the number of delay line taps required to effectively mitigate the effect of multiple interferers increases as the number of interferers and array elements increases. For example, a 3-element array needs only 3 taps per element while a 6-element array needs 9 taps per element for interference mitigation.

Interference Characterization and Mitigation of 5.5 Mbps CCK WI-FI Signals

An exact power spectral density (PSD) expression is derived for IEEE 802.11b 5.5 Mbps signals using complementary code keying (CCK). The analytical result obtained is verified through computer simulation. The spectral signature of the 5.5 Mbps CCK- modulated signal is compared to the PSD of the Barker-spread Wi-Fi signals. The adjacent channel interference power resulting from the 5.5 Mbps CCK interferer is introduced and compared to that caused by Barker-spread signals. Adaptive antennas with tapped delay lines are used to mitigate the effect of these interference signals. Optimal ranges of the tapped delay lines are found such that performance is restored at minimum cost.

Multi-element adaptive arrays for interference mitigation of multiple barker/CCK signals in 802.11b WLANs

We analyze interference in the unlicensed ISM wireless band for IEEE 802.11 barker-code spread and Complementary Code Keying spread Wireless Fidelity signals and contrast the results to that of narrowband interferers. Multi-element adaptive antennas with tapped-delay-lines are used to mitigate multiple interferers. It is shown that the number of delay line taps required to successfully mitigate the effect of multiple interferers increases as the number of interferers and array elements increases.