OFDMA_Part39

# OFDMA_Part39 - to Figure 11 is a very interesting problem....

This preview shows page 1. Sign up to view the full content.

39 The following optimization problem, constrained by E15 and E31, illustrates the basic idea of the RA approach for the multi-user system being considered [26]: max c k , n , p n c k , n × F ( SNR k , n , P e ) n k …(E32) where SNR k , n = p n × h k , n 2 σ 2 …(E33) In the above equations, the function F provides the achievable data rate per subcarrier for a given signal-to-noise-ratio ( SNR ), modulation scheme, and probability of bit-error ( P e ). Many RA algorithms often impose the following constraint (in addition to the constraints mentioned above) to ensure that the data rate of each user k is greater than or equal to the minimum required data rate for the user, i.e. R k [26]: r k R k , k …(E34) where r k = c k , n × F ( SNR k , n , P e ) n …(E35) Now that I have defined the RA problem for the single-user and multi-user scenarios, let us consider some real-world RA algorithms to better understand rate-adaptive resource allocation in OFDMA systems. Please note that the single-user problem was posed only for illustration purposes and its solution is trivial. However, the multi-user problem that was posed in reference
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: to Figure 11 is a very interesting problem. All the real-world algorithms surveyed in the following subsection try to solve this problem by using different flavors of the RA approach. 4.1.3.1 Survey Of Rate Adaptive Resource Allocation Algorithms In [34], Yin and Liu’s algorithm performs OFDMA resource allocation for a system like the one shown in Figure 11 in two steps. The first step (shown in Figure 19) determines the number of subcarriers to be assigned to each user and the amount of power to be allocated to each subcarrier. The second step uses the Hungarian method [35] to make subcarrier assignments and loads bits onto each subcarrier. In the first step, the idea is to gradually increase the number of subcarriers assigned to each user. In Box (1) of Figure 19, each user m is assigned a single carrier to begin with. After the first...
View Full Document

## This note was uploaded on 09/27/2009 for the course ECE 399 taught by Professor Prof during the Spring '09 term at University of Texas.

Ask a homework question - tutors are online