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Abstract-In this paper, a new wide-band mobile channel emulator for the CODIT project is designed and implemented. The UMTS code-division testbed (CODIT R2020) is a research project within the European RACE-II program set up by the Commission of the European Community. Our goal is to be able to simulate in the laboratory, in real time, the multipath propagation found in the mobile radio channel. As code-division multiple access (CDMA) is the access technique within the CODIT project, it was realized that the channel emulator must have simultaneously good delay resolution between propagation paths and long duration of the impulse response. These considerations led to a very flexible channel emulator specifically designed to host the new wideband channel models developed within the CODIT project. Our emulator features three independent inputs and two outputs, up to 20 complex propagation paths, 10-MHz radio frequency (RF) bandwidth, a delay resolution of 50 ns, and a maximum duration of the channel impulse response of 80 s. Starting with an explanation of the global structure of the new channel emulator, we derive the optimum design of the interpolation procedures and present the main implementation issues arising from our initial architecture. Finally, we report the results of the laboratory tests of the first prototype of the channel emulator.

The paper presents a two-step technique for real-time track detection in single-track railway sidings using low-cost MEMS gyroscopes. The objective is to reliably know the path the train has taken in a switch, diverted or main road, immediately after the train head leaves the switch. The signal delivered by the gyroscope is first processed by an adaptive low-pass filter that rejects noise and converts the temporal turn rate data in degree/second units into spatial turn rate data in degree/meter. The conversion is based on the travelled distance taken from odometer data. The filter is implemented to achieve a speed-dependent cut-off frequency to maximize the signal-to-noise ratio. Although direct comparison of the filtered turn rate signal with a predetermined threshold is possible, the paper shows that better detection performance can be achieved by processing the turn rate signal with a filter matched to the rail switch curvature parameters. Implementation aspects of the track detector have been optimized for real-time operation. The detector has been tested with both simulated data and real data acquired in railway campaigns.

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Software-defined radio (SDR) describes radio transceivers implemented in software that executes on general-purpose hardware. SDR combined with cloud computing technology will reshape the wireless access infrastructure, enabling computing resource sharing and centralized digital-signal processing (DSP). SDR clouds have different constraints than general-purpose grids or clouds: real-time response to user session requests and real-time execution of the corresponding DSP chains. This article addresses the SDR cloud computing resource management problem. We show that the maximum traffic load that a single resource allocator (RA) can handle is limited. It is a function of the RA complexity and the call setup delay and user blocking probability constraints. We derive the RA capacity analytically and provide numerical examples. The analysis demonstrates the fundamental tradeoffs between short call setup delays (few processors) and low blocking probability (many processors). The simulation results demonstrate the feasibility of a distributed resource management and the necessity of adapting the processor assignment to RAs according to the given traffic load distribution. These results provide new insights and guidelines for designing data centers and distributed resource management methods for SDR clouds.

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This paper describes the motivation, methodology and implementation approach of the testbed that has been developed in the framework of the EVEREST project. Such testbed is used for demonstrating some of the main concepts addressed within the project, concerning both: Common Radio Resource Management strategies and end-to-end QoS architectures and mechanisms for B3G systems based on the UMTS architecture. The complexity of the interaction between B3G systems and the user applications, while dealing with the QoS concept, pushes to develop this kind of emulation platforms, where algorithms and applications can/must be tested in realistic conditions, not achievable by means of off-line simulations.

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