Software radio architecture with smart antennas: a tutorial on algorithms and complexity

Abstract

Abstract-Recently, there has been considerable interest in using antenna arrays in wireless communication networks to increase the capacity and decrease the cochannel interference. Adaptive beamforming with smart antennas at the receiver increases the carrier-to-interference ratio (CIR) in a wireless link. This paper considers a wireless network with beamforming capabilities at the receiver which allows two or more transmitters to share the same channel to communicate with the base station. The concrete computational complexity and algorithm structure of a base station are considered in terms of a software radio system model, initially with an omnidirectional antenna. The software radio computational model is then expanded to characterize a network with smart antennas. The application of the software radio smart antenna is demonstrated through two examples. First, traffic improvement in a network with a smart antenna is considered, and the implementation of a hand-off algorithm in the software radio is presented. The blocking probabilities of the calls and total carried traffic in the system under different traffic policies are derived. The analytical and numerical results show that adaptive beamforming at the receiver reduces the probability of blocking and forced termination of the calls and increases the total carried traffic in the system. Then, a joint beamforming and power control algorithm is implemented in a software radio smart antenna in a CDMA network. This shows that, by using smart antennas, each user can transmit with much lower power, and therefore the system capacity increases significantly.Index Terms-Adaptive beamforming, handoff, power control, smart antennas, software radio.

Blind Signal Separation for Cognitive Radio

“…Multiple-antenna is necessary for the transmitter to generate beam patterns and for the receiver to make use of the phase difference. Letŵ be the optimal weighting vector of the beamformer, an example of receiver beamforming is [25] …”

“…This usually requires the knowledge of channel condition and even other user's messages. Interference to other users can also be mitigated using beamforming [8,20,25]. At the mean time of signal transmission, the spectrum sensing function keeps tracking spectrum activities.…”

Receiver-Oriented Multiple Access in Ad Hoc Networks with Directional Antennas

“…If the mode depends on criterion (a) alone (ROMA lines 1-7), there is positive probability that all nodes in the network be assigned the same mode, which causes deadlock in channel access. Criterion (b) allows some nodes to flip their modes to break the deadlock (ROMA lines [8][9][10][11][12][13][14][15]. Because ROMA requires receiving nodes to listen to the top K incoming links, regardless of the modes of the heads for those links (ROMA lines 16-28), there are always active links in the network at any time slot.…”

“…Similarly, the receiver can enhance the sensitivity of the antenna in certain directions, thus eliminating many of the multipath effects and co-channel interference (CCI). With M antenna elements, an antenna array generally provides an increased antenna gain of M plus a diversity gain against multipath fading [12,16]. When a constant signal gain is maintained along the direction of interest and the nulls are adjusted toward the sources of interference so as to reject CCI, it can dramatically increase the performance characteristics of a wireless system in its capacity, coverage, and quality.…”

Adaptive joint beamforming and B‐MMSE detection for CDMA signal reception under multipath interference

“…The authors succeeded in deriving a new upper bound on block error rate with the consideration to imperfect channel estimates. Razavilar et al in their paper [5] offered a comprehensive tutorial on smart antenna systems with software radio implementations. The paper also, in particular, addressed the issues on adaptive beamforming.…”