# A Survey of Resource Allocation Techniques for Cellular Network's Operation in the Unlicensed Band
## 7 LTE-U's Evaluation in Diverse Traffic Type, Environments, and Scenarios  
The LTE-U performance for a full buffer or saturated mode has been analyzed in [39; 53] for downlink traffic with time division duplexing (TDD). A similar analysis for LTE-U with full buffer downlink and frequency division duplexing (FDD) has been performed in [31]. However, a joint analysis for LTE-U comparing downlink traffic with a full buffer for both FDD and TDD is not available. A significant number of works as shown in Table 2 consider the saturated traffic conditions but do not clearly demarcate the TDD or FDD as the duplexing mode. Furthermore, in the full buffer scenario, no analysis is available for LTE-U with uplink traffic.  
In contrast with the full buffer mode, unsaturated traffic conditions for uplink traffic with TDM have been studied in [81] for an FBE. The impact of co-existence of WLAN and LTE-U for FTP and VoIP Packet data at WLAN and downlink FTP data at LTE-U has been analyzed in [69]. In [43], both FTP and VoIP data over the LTE-U downlink have been analyzed in the presence of both uplink and downlink packet transfer in the WLAN. FTP data based downlink data traffic for LTE and WLAN have been considered in [84]. Although [54; 71; 86] consider models that are inspired by unsaturated traffic conditions, more detailed study of LTE-U with various channel access mechanisms and channel selection schemes in the presence of diverse traffic type is required.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Buffer** & **Uplink Downlink** & **Comment** & **References** \\ \hline \multirow{4}{*}{Saturated} & Uplink & NA & [50] \\ \cline{2-4}  & \multirow{3}{*}{Downlink} & TDD & [39; 53] \\ \cline{3-4}  & & FDD & [31] \\ \cline{3-4}  & & Not specified & [6; 7; 8; 20; 21; 29; 35; 44; 50; 57; 60; 66; 67; 76; 82; 83] \\ \hline \multirow{4}{*}{Non-saturated} & Uplink & TDM & [81] \\ \cline{2-4}  & \multirow{3}{*}{Downlink} & Voice traffic & [14; 27; 43; 69] \\ \cline{1-1} \cline{3-4}  & & FTP traffic & [14; 69; 84] \\ \cline{1-1} \cline{3-4}  & & Not specified & [6; 40; 48; 58; 68; 70; 78; 85] \\ \cline{1-1} \cline{2-4}  & \multicolumn{2}{c}{Not specified} & [54; 71; 86] \\ \hline \hline \end{tabular}
\end{table}
Table 2: A summary of traffic models studied for LTE-U.  
The performance of LTE-U based SCs in the presence of WLAN has been evaluated for both indoor and outdoor environments in [43; 60; 64; 70; 71]. A thorough evaluation specifically for indoor deployment of LTE-U based SCs has been considered in [3; 39; 44; 46; 68; 69; 53]. However, in depth studies for outdoor deployment of LTE-U SCs coexisting with WLAN has been analyzed in [7; 84; 83; 80]. The work in [80] in particular presents results consider realistic deployments of LTE-U based SCs.  
Most of the simulation based studies for LTE-U like [3; 4; 7; 60] have considered MATLAB as the simulation environment. However, packet level simulation with the LTE-LENA stack and NS have been considered in [87]. The WaltSystem and WinProp based simulation results have been shown in [57; 86], respectively, while [80] presents simulation results for both MATLAB and WinProp based simulations. Detailed hardware based implementation of LTE-U using USRPs and the ORBIT testbed has been considered in [39]. Similarly, NTT DOCOMO and Huawei's field trial results using proposed LTE-U hardware has been shown in [53]. Details of various simulation, hardware, traffic environments, and scenarios considered are summarized in Tables 2 and 3. Next, we consider the important issues of latency and handover analysis for LTE-U based SCs.