English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We consider multi-antenna base stations using orthogonal frequency divisionmultiple access and space division multiple access techniques to servesingle-antenna users. Some users, called real-time users, have minimum raterequirements and must be served in the current time slot while others, callednon real-time users, do not have strict timing constraints and are served on abest-effort basis. The resource allocation problem is to find the assignment ofusers to subcarriers and the transmit beamforming vectors that maximize thetotal user rates subject to power and minimum rate constraints. In general,this is a nonlinear and non-convex program and the zero-forcing technique usedhere makes it integer as well, exact optimal solutions cannot be computed inreasonable time for realistic cases. For this reason, we present a technique tocompute both upper and lower bounds and show that these are quite close forsome realistic cases.  First, we formulate the dual problem whose optimum provides an upper bound toall feasible solutions. We then use a simple method to get a primal-feasiblepoint starting from the dual optimal solution, which is a lower bound on theprimal optimal solution. Numerical results for several cases show that the twobounds are close so that the dual method can be used to benchmark any heuristicused to solve this problem. As an example, we provide numerical results showingthe performance gap of the well-known weight adjustment method and show thatthere is considerable room for improvement.

Dual-Based Bounds for Resource Allocation in Zero-forcing Beamforming OFDMA-SDMA Systems