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Modified Cramer-Rao bounds (MCRB) and asymptotic Cramer-Rao bounds (ACRB) are derived and investigated for frequency estimation in systems with transmission through parallel fading channels. The bounds are derived for arbitrary correlation of fading processes and arbitrary pilot signals and the results are applicable to communications in multipath, multiantenna and fast fading channels, and any combination of these channel types.

We propose and evaluate a vertical handover mechanism for TCP, based on receiver bandwidth delay product (BDP) measurement and congestion control using the receiver's advertised window. It addresses the negative impact of abrupt changes in link capacity and latency on TCP performance during make-before-break vertical handover in heterogeneous networks, enabling TCP to seamlessly adapt to new conditions. It resolves the problem of buffer overflow in a low capacity network on handover from a high capacity network, and the under-utilisation problem on handover in the reverse direction. All modifications are restricted to the mobile device, and the proposed technique is fully interoperable with existing TCP and mobile IP infrastructure. It maintains end-to-end semantics, supports IP security, and can be easily deployed [ABSTRACT FROM PUBLISHER]