Channel Selection Metric by the Number of Users and SNR in WLAN In this paper, a channel selection metric is presented for WLAN. It is based on SNR and the number of users. A delay time is employed to define metric of channel selection. Nthorder polynomials are introduced to obtain a polynomial metric in a tractable form. The advantage of formulation is that more parameters other than SNR or the number of users can be added to metric without taking up complex delay analysis. Numerical results are presented to demonstrate metric as a function of SNR and the number of users. The effective range of metric is discussed with a difference between the polynomial and delay time metrics.

Modified SNR Gap Approximation for Resource Allocation in LDPCCoded Multicarrier Systems The signaltonoise ratio (SNR) gap approximation provides a closedform expression for the SNR required for a coded modulation system to achieve a given target error performance for a given constellation size. This approximation has been widely used for resource allocation in the context of trelliscoded multicarrier systems (e.g., for digital subscriber line communication). In this contribution, we show that the SNR gap approximation does not accurately model the relation between constellation size and required SNR in lowdensity paritycheck (LDPC) coded multicarrier systems. We solve this problem by using a simple modification   the SNR gap approximation instead, which fully retains the analytical convenience of the former approximation. The performance advantage resulting from the proposed modification is illustrated for singleuser digital subscriber line transmission.