Barry G. Evans

A Survey of Self Organisation in Future Cellular Networks

This article surveys the literature over the period of the last decade on the emerging field of self organisation as applied to wireless cellular communication networks. Self organisation has been extensively studied and applied in adhoc networks, wireless sensor networks and autonomic computer networks; however in the context of wireless cellular networks, this is the first attempt to put in perspective the various efforts in form of a tutorial/survey. We provide a comprehensive survey of the existing literature, projects and standards in self organising cellular networks. Additionally, we also aim to present a clear understanding of this active research area, identifying a clear taxonomy and guidelines for design of self organising mechanisms. We compare strength and weakness of existing solutions and highlight the key research areas for further development. This paper serves as a guide and a starting point for anyone willing to delve into research on self organisation in wireless cellular communication networks.

Integration of satellite and terrestrial systems in future multimedia communications

In this article we examine the role of satellite communications in future telecommunication networks and service provision. Lessons from the past indicate that satellites are successful as a result of their wide area coverage or speed to market for new services. Niche areas such as coverage of air and sea will persist, but for land masses convergence of fixed, mobile, and broadcasting will dictate that the only way forward for satellites is in an integrated format with terrestrial systems. We outline future ways forward for satellites, and discuss the research challenges and technology advances needed to facilitate this integrated approach.

Robust time-domain timing and frequency synchronization for OFDM systems

A robust and efficient technique for frame/symbol timing and carrier frequency synchronization in OFDM systems is presented. It uses a preamble consisting of only one training symbol with two identical parts to achieve reliable timing and frequency accuracy in the time-domain, over a wide frequency estimation range which can be up to half of the signal sampling frequency. Also, it has a low complexity which is adaptive to the degree of channel distortion. Computer simulations in the Rayleigh fading ISI channel show that the proposed method achieves superior performance to existing techniques in terms of timing and frequency accuracy. Also, its operation in the time-domain helps to achieve faster synchronization convergence.

Cognitive spectrum utilization in Ka band multibeam satellite communications

Multibeam satellite networks in Ka band have been designed to accommodate the increasing traffic demands expected in the future. However, these systems are spectrum limited due to the current spectrum allocation policies. This paper investigates the potential of applying cognitive radio techniques in satellite communications (SatCom) in order to increase the spectrum opportunities for future generations of satellite networks without interfering with the operation of incumbent services. These extra spectrum opportunities can potentially amount to 2.4 GHz of bandwidth in the downlink and 2 GHz of bandwidth in the uplink for high density fixed satellite services (HDFSS).

Protocol architectures for satellite ATM broadband networks

The latest developments and experimentation in asynchronous transfer mode (ATM) technology show that ATM will be a candidate transport mechanism in many private and public multimedia networks. Furthermore, the interest in satellite ATM systems has grown considerably because they can rapidly and economically extend the boundaries of any terrestrial network. Currently, there is a huge increase in the demand for satellite communications operating at the Ka-frequency bands; several different systems have been proposed and are under development worldwide. Two main scenarios for satellite access network protocols are presented in this article. The first one uses ATM cell encapsulation and satellite-specific protocols for establishing and managing a connection, whereas the second one provides a highly integrated solution with the ATM protocol stack and defines a new satellite ATM (S-ATM) protocol layer.

Improved preamble-aided timing estimation for OFDM systems

An improved method for estimating the frame/symbol timing offset in preamble-aided OFDM systems is presented. It uses a conventional preamble structure and combines autocorrelation techniques with restricted crosscorrelation to achieve a near-ideal timing performance without significant increase in complexity. Computer simulations show that the method is robust in both AWGN and fading multipath channels, achieving better performance than the existing methods.

Narrowband channel statistics from multiband propagation measurements applicable to high elevation angle land-mobile satellite systems

Results from a multiband propagation experiment for a high elevation angle land-mobile satellite (LMS) channel are presented. A small helicopter was used to fly the transmitter module, transmitting frequencies in the L, S, and Ku bands. A vehicle equipped with the corresponding receivers and data acquisition system was followed by the helicopter on the selected routes. The measurement campaign was undertaken in two phases in September 1991 and in April 1992. The results show considerable decrease in signal attenuation when the path elevation angle is high due to reduced shadowing. In general, the attenuation increases with the increasing radio frequency. Foliage density has also been found to influence the fade levels, especially at higher path elevation angles. The overall analysis of the propagation data indicates that the fading character of the LMS channel is significantly dependent on the surrounding environment. >

Cognitive radio scenarios for satellite communications: The CoRaSat approach

This paper presents initial results of the recently kicked-off FP7 ICT STREP project “CoRaSat” (Cognitive Radio for Satellite Communications) [1]. Focus is put on the preliminary identification of the scenarios which are suitable for the applicability of Cognitive Radio technology over Satellite Communications (SatCom). The considered frequency bands include Ka-band, Ku-band, C-band and S-band, where regulatory and coordination constraints exist. An initial mapping of broadband and narrowband SatCom use cases on each identified scenario is also provided. Moreover, several challenges associated to the applicability of Cognitive Radio over SatCom in the identified scenarios are presented, which form the basis of the market/business, regulatory, standardization and technological framework of CoRaSat. Furthermore, ongoing and future work of the CoRaSat project is outlined.

Connection admission control strategy and routing considerations in multimedia (non-geo) satellite networks

This paper investigates the strategy that has to be adopted for connection admission control and handoff execution in dynamic satellite networks that use on board satellite fast packet switching as part of a mobile broadband ISDN network. A new method for admission control and radio resource management in a multispot-beam satellite network is proposed and its performance is examined by a simulation model. The results show that we can implement a flexible connection admission control algorithm in a distributed way that take the user mobility in addition to the service specific parameters in account.

A terabit/second satellite system for European broadband access: a feasibility study

This paper presents a feasibility study for a fixed broadband access High Throughput Satellite terabit/second system by considering appropriate state‐of‐the‐art communication technologies. For the investigated system model, DVB‐S2 and DVB‐RCS2 are assumed as the air interfaces for the forward and return link, respectively. The performance of DVB‐S2 and DVB‐RCS2 Adaptive Coding and Modulation is examined along with potential extensions of these standards. For example, the performance of very low rate DVB‐RCS turbo codes are investigated and their performance is evaluated. In addition, a performance comparison for M‐ary (M=16, 32, 64) constellations in the presence of a linear and a high power amplifier non‐linear channel is carried out. Various frequency reuse schemes and different antenna models are also considered, and their performance is analyzed and evaluated. It is demonstrated that, by using the Q/V (40/50 GHz) bands for the gateways and the Ka (20–30 GHz) band for the user terminals, around 20 gateways and 200 beams are required to provide with the proposed satellite system terabit/second capacity. The obtained performance evaluation results have shown that the forward link is limited by noise rather than interference, whereas the return link is interference limited. Additionally, some further aspects of the system design in relation with the total number of gateways and the payload are discussed.