Multi‐Carrier and Spread Spectrum Systems

Network Efficient Power Control for Wireless Communication Systems

“…However, it is assumed that F 2 is a multiple of F 1 to facilitate the implementation; that is, m ≜ F 2 / F 1 ∈ ℤ . On the other hand, the network optimization is focused on a CDMA-based network, where DS-CDMA and MC-CDMA are two important CDMA schemes for high rate wireless communications and therefore we aim our study on these schemes [2, 5, 23, 24]. Since the maximization problem will be solved in a distributed fashion, the index l related to each BS in the wireless network will be omitted.…”

“…The load percentage of the CDMA-based system is defined as the ratio 100% × U / N . In this way, assuming users synchronization, the received signal r [ k ] at k -time instant in the BS (uplink transmission) after sampling and demodulation is given by [2, 5, 23] $\begin{array}{c}\mathbf{r}\left[k\right]=\mathbf{C}\mathrm{\hspace{0.17em}\hspace{0.17em}}\mathrm{\Gamma }\left[k\right]\mathbf{b}\left[k\right]+\mathbf{\eta }\left[k\right],\end{array}$ where, in the case of DS-CDMA, matrices C and Γ[ k ] are given by $\begin{array}{c}\mathbf{C}=\left[\begin{array}{ccc}{\mathrm{boldc}}_{\mathrm{normal1}}& \cdots & {\mathrm{boldc}}_U\end{array}\right]=\left[\begin{array}{ccc}{c}_{\mathrm{normal1,1}}& \cdots & c_{U,\mathrm{normal1}}\\ ⋮& \ddots & ⋮\\ c_{\mathrm{normal1},N}& \cdots & c_{U,N}\end{array}\right]\in {ℝ}^{N\times U},\\ \mathrm{\Gamma }\left[k\right]=\left[\begin{array}{ccc}{h}_{\mathrm{normal1}}\left[k\right]\sqrt{p_1\left[k\right]}& & \\ & \ddots & \\ & & h_U\left[k\right]\sqrt{p_U\left[k\right]}\end{array}\right]\in {ℂ}^{U\times U},\end{array}$ where h j [ k ] ∈ ℂ and $\sqrt{p_j[k]}\in ℝ$ denote the channel gain and transmission power factor for the j th user, respectively; b [ k ] = [ b 1 [ k ]  ⋯   b U [ k ]] ⊤ ∈ ℂ U represents the vector of data symbols; each symbol b j [ k ] for all j = 1,…, U has zero mean and normalized energy, that is, ℰ { b j [ k ]} = 0 and ℰ {| b j [ k ]| 2 } = 1, and η [ k ] ∈ ℂ N represents a vector with zero-mean complex Gaussian noise components of variance σ 2 per dimension; that is, ℰ { η [ k ]} = 0, ℰ { η [ k ]* η [ k ]} = σ 2 I   ∀ k . For practical implications, all the power factors are restricted to a feasible interval; that is, $\begin{array}{c}{p}_{\min }\le p_j\left[k\right]\le p_{\max },\hspace{1em}\forall j=\mathrm{}\end{array}$…”

“…This work focuses on a CDMA-based network [2, 23] such as direct-sequence CDMA (DS-CDMA) or multicarrier CDMA (MC-CDMA), since it comprises all varieties of systems impairments (multiple access interference, multipath, etc.) which makes a CDMA network more challenging than any other access techniques even those that are currently under consideration for 4G systems.…”

“…which makes a CDMA network more challenging than any other access techniques even those that are currently under consideration for 4G systems. However, and more importantly, the proposed mechanism can be extended to other access techniques, such as orthogonal frequency-division multiplexing (OFDM) [23, 24], as long as the SINR or SNR are employed as a QoS measure. Since any CDMA-based network capacity is interference limited [2, 23, 24], interference management is needed to maximize its performance.…”

“…However, and more importantly, the proposed mechanism can be extended to other access techniques, such as orthogonal frequency-division multiplexing (OFDM) [23, 24], as long as the SINR or SNR are employed as a QoS measure. Since any CDMA-based network capacity is interference limited [2, 23, 24], interference management is needed to maximize its performance. To manage the power consumption in the terminals, we formulate an overall power consumption index based on the whole power of the terminal and not just the radiated power, which makes this index strongly dependent on the detection strategy.…”