Abstract
Ultra-wideband (UWB) wireless communication systems are based on the transmission of extremely narrow pulses, with a duration inferior to a nanosecond. The application of transmit reference (TR) to UWB systems allows to side-step channel estimation at the receiver, with a tradeoff of the effective transmission bandwidth, which is reduced by the usage of a reference pulse. Similar to CDMA systems, different users can share the same available bandwidth by means of different spreading codes. This allows the receiver to separate users, and to recover the timing information of the transmitted data packets. The nature of UWB transmissions—short, burst-like packets—requires a fast synchronization algorithm, that can accommodate several asynchronous users. Exploiting the fact that a shift in time corresponds to a phase rotation in the frequency domain, a blind and computationally effcient synchronization algorithm that takes advantage of the shift invariance structure in the frequency domain is proposed in this paper. Integer and fractional delay estimations are considered, along with a subsequent symbol estimation step. This results in a collision-avoiding multiuser algorithm, readily applicable to a fast acquisition procedure in a UWB ad hoc network.
Highlights
Impulse radio (IR) ultra-wideband (UWB), further on called UWB, has recently been proposed as a system that can provide high data rate communications on short distances
Observe that the presented data model resembles a conventional data model for DS-CDMA, up to the channel gain (A) and DC offset (b) term of the channel correlation. This will allow us to use synchronization methods similar in spirit to the DS-CDMA synchronization methods. Before we introduce these synchronization methods, we first generalize the above model to a data model for multiple transmitted data symbols
We begin with defining the second block column Zτ, which is similar to the first block column of (19): Zτ = [0Tκ×M, ZT, 0T(K−κ)×M]T
Summary
Impulse radio (IR) ultra-wideband (UWB), further on called UWB, has recently been proposed as a system that can provide high data rate communications (up to 100 Mbit/s) on short distances (order of 10 m). Generation of the pulses is an extremely low-complexity and low-power operation [2] and facilitates the accomplishment of low-cost transmitter devices All these features make impulse radio attractive for high data rate, short distance, and multiuser personal area networks (PAN). Performing an exhaustive search over different delays, averaging over several data symbols and searching for the maximum of the recollected energy function provide the estimate of the packet offset Note that for this kind of receiver the knowledge of the channel is required. Some authors propose the implementation of a RAKE receiver to obtain the estimate of the channel but taking into account the current state of technology, we consider this approach unsuitable for implementation in a low-cost UWB transceiver because of the high computational complexity and high sampling rates. Diag(v) is a diagonal matrix with the entries of v on the diagonal. ⊗ is the Kronecker product. vec(A) is a stacking of the columns of matrix A into a vector
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