Channel Equalization in Fast-Convolution Filter Bank based Receivers for Professional Mobile Radio

Abstract-Fast convolution processing has recently been proposed as an efficient approach for implementing filter bank multicarrier systems with good spectral containment and high flexibility in adjusting the subchannel bandwidths and center frequencies. These features make fast convolution filter banks (FC-FBs) a particularly interesting choice for multicarrier transmission in challenging radio scenarios like dynamic spectrum access, cognitive radio, and fragmented spectrum use. In this contribution, the target is to compare the performance of the time-domain equalizer with the frequency-domain equalizer implemented through subcarrier processing in LTE-like multicarrier systems. It is shown that integrating the equalization functions with the FC-FB processing leads to an efficient overall implementation in terms of performance and computational complexity

A taxonomy and evaluation for developing 802.11‐based wireless mesh network testbeds

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92433/1/dac1299.pd

Large-Scale Site and Frequency Diversity in Urban Peer-to-Peer Channels for Six Public Safety Frequency Bands

We report on peer-to-peer large-scale wireless channel characteristics for an urban environment in six public-safety bands, for five simultaneous receiving sites. Results are based upon measurements taken in Denver in July 2009 with stationary receivers and a pedestrian transmitter. The six frequencies at which we measured are (in MHz) 430, 750, 905, 1834, 2400, and 4860. We quantify both site and frequency diversity, and show that 5-site selection yields minimum average gains of 15 dB in mean received power levels; 5-site selection diversity also reduces received power variation by 17-29 dB, depending on frequency. Frequency diversity yields similar gains. By approximating received powers as lognormal, we describe an analytical method to approximate the cdf of the per-site, or per-frequency (or both) maximum received power. These data and diversity models should be useful for public-safety and ad hoc communication system designers, and for cooperative diversity schemes, wherein multiple users act as a virtual array

Feasibility study of IP Multimedia Subsystem (IMS) based Push-to-Talk over Cellular (PoC) for public safety and security communications

Feasibility of IMS based PoC over public cellular network, specifically over commercial GPRS network, has been studied for public safety and security communication. Both day-to-day routine work and emergency operation handling capability of the PoC service as well as of the network have been considered. The requirements of PSS communication have been taken as the basis for analysing the technical viability of PoC service for PSS communication. The study is based on publicly available specification documents and related literature. The technical data and factual information have been collected from technical papers, reports and news articles posted into the Internet. The thesis also included a case study comparing over-aged analogue PMR systems and possible PoC service over a nationwide commercial GSM/GPRS network for PSS communication. The key findings in favour of using PoC over commercial GPRS networks include already existed nation-wide radio coverage and roaming across the nation boarder, ease of use, special group call functionality, advanced IMS based multimedia services. The study has identified some challenges of using PoC for PSS communication, which are mainly due to the inherent latency of GPRS access network and lack of prioritisation of special groups of users in commercial networks. Though the PoC service over commercial network does not fulfil all the requirements strictly but taking into account the suggested measures, it can be a good alternative to PMR networks. Use of PoC for PSS communication requires zero initial as well as less operational expenses for the respective PSS organizations. At the same time PSS sector is a potential revenue generating market segment for the operator as well

Enhanced OFDM for fragmented spectrum use

OFDM, as a multiplexing and modulation scheme, transmits digital data on orthogonal subcarriers saving spectral bandwidth. OFDM scheme offers high level of adaptivity through spectral fragmentation. Hence, each subcarrier can be modulated and coded independently according to the channel situation and users’ requirements. Generally, advanced cognitive radio, dynamic spectrum use and fragmented coexistence scenarios consider OFDM as the first candidate technology to employ the available spectral gaps effectively. Nevertheless, OFDM scheme leaks high power sidelobes in the unused part of the spectrum. This limits the spectral use near the active subcarriers This thesis is in the context of sidelobe suppression in OFDM schemes, discussing four different suppression techniques, i.e., time domain windowing, cancellation carrier, subcarrier weighting and polynomial cancellation coding. Consequently, the four represented techniques are applied on a practical 5 MHz 3GPP LTE scenario. Finally, the required tradeoffs for each technique are evaluated. The target of this research is to properly elaborate the selected techniques for suppressing the sidelobes in contiguous and non-contiguous cases and without causing severe side effects to the OFDM model. The contributions of this thesis include improvements to the edge windowing and cancellation carrier techniques, enhancing their suppression performance and reducing their limitations