INTRODUCTION
KNOWING the channel profile is very useful in order to maximize performance or minimize interferences in a wireless communication environment. There are several parameters which have to be properly set in the receiver depending on the link condition (LOS, Quasi-LOS, NLOS,extreme NLOS): for example the time delays and amplitudes of the channel multipath estimation algorithm, the number of fingers of the rake receiver, etc. The channel parameters (delay and amplitude of the receiving paths) estimation algorithm is particularly sensitive to the link condition. This means that if a simpler algorithm is selected under LOS conditions, the algorithm under NLOS conditions must be more complex in order to guarantee the performance. Similarly, the number of fingers of the rake receiver has to be selected depending on the link condition in order to achieve quality with lowest complexity.
Unfortunately it is not easy to identify the channel. In the literature there are few papers proposing parameters that allow to distinguish only between the LOS and the NLOS condition. Therefore, the present paper has a twofold aim: on the one hand, it intends to search for a new index that allows to distinguish more precisely between LOS and NLOS in every environment, and, furthermore, between different LOS or NLOS conditions, creating a sub-set of LOS links and NLOS links ordered with an increasing quality; on the other hand it aims at defining a low complex parameter that allows the identification of the quality of the received signal in an UWB indoor environment.
KNOWING the channel profile is very useful in order to maximize performance or minimize interferences in a wireless communication environment. There are several parameters which have to be properly set in the receiver depending on the link condition (LOS, Quasi-LOS, NLOS,extreme NLOS): for example the time delays and amplitudes of the channel multipath estimation algorithm, the number of fingers of the rake receiver, etc. The channel parameters (delay and amplitude of the receiving paths) estimation algorithm is particularly sensitive to the link condition. This means that if a simpler algorithm is selected under LOS conditions, the algorithm under NLOS conditions must be more complex in order to guarantee the performance. Similarly, the number of fingers of the rake receiver has to be selected depending on the link condition in order to achieve quality with lowest complexity.
Unfortunately it is not easy to identify the channel. In the literature there are few papers proposing parameters that allow to distinguish only between the LOS and the NLOS condition. Therefore, the present paper has a twofold aim: on the one hand, it intends to search for a new index that allows to distinguish more precisely between LOS and NLOS in every environment, and, furthermore, between different LOS or NLOS conditions, creating a sub-set of LOS links and NLOS links ordered with an increasing quality; on the other hand it aims at defining a low complex parameter that allows the identification of the quality of the received signal in an UWB indoor environment.
Algorithms for NLOS identification are proposed. The Time-Of-Arrival (TOA) of the signal is studied in order to identify if a mobile station is experiencing LOS or NLOS condition. In particular, the TOA measured probability distribution function has been considered. In, a joint power envelope and TOA measured algorithms are proposed to distinguish between LOS and NLOS. All the algorithms mentioned above have quite high complexity and it is necessary to estimate the channel parameters in order to apply the algorithm. In particular, multipath time delays are needed in , whereas in multipath amplitudes are needed. Moreover, both those algorithms can distinguish only LOS/NLOS condition
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