LTE 4G is the next generation of cellular network which specifically aims to improve the network performance for data traffic and is currently being rolled out by many network operators. We present results from an extensive LTE measurement campaign in Dublin, Ireland using a custom performance measurement tool. Performance data was measured at a variety of locations within the city (including cell edge locations, indoors, outdoors etc) as well as for mobile users on public transport within the city. Using this data we derive a model of the characteristics of link layer RTT and bandwidth vs link signal strength. This model is suited to use for performance evaluation of applications and services, and since it is based on real measurements it allows realistic evaluation of performance.
A number of other studies measure throughput and or latency information, but tend to focus on their impact on TCP or its derivatives @cite_19 @cite_14 @cite_6 @cite_8 @cite_11 @cite_5 @cite_12 . Additionally, there are studies that present measurements but do not use these to develop a model suited to performance evaluation @cite_18 .
@cite_18 @cite_14 @cite_8 @cite_6 @cite_19 @cite_5 @cite_12 @cite_11
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The performance of Internet services is intrinsically tied to propagation delays between end points (i.e., network latency). Standard active probe-based or passive host-based methods for measuring end-to-end latency are difficult to deploy at scale and typically offer limited precision and accuracy. In this paper, we investigate a novel but non-obvious source of latency measurement---logs from network time protocol (NTP) servers. Using NTP-derived data for studying latency is compelling due to NTP's pervasive use in the Internet and its inherent focus on accurate end-to-end delay estimation. We consider the efficacy of an NTP-based approach for studying propagation delays by analyzing logs collected from 10 NTP servers distributed across the United States. These logs include over 73M latency measurements to 7.4M worldwide clients (as indicated by unique IP addresses) collected over the period of one day. Our initial analysis of the general characteristics of propagation delays derived from the log data reveals that delay measurements from NTP must be carefully filtered in order to extract accurate results. We develop a filtering process that removes measurements that are likely to be inaccurate. After applying our filter to NTP measurements, we report on the scope and reach for US-based clients and the characteristics of the end-to-end latency for those clients. In recent years the research community has developed many techniques to estimate the end-to-end available bandwidth of an Internet path. This important metric can be potentially exploited to optimize the performance of several distributed systems and, even, to improve the effectiveness of the congestion control mechanism of TCP. Thus, it has been suggested that some existing estimation techniques could be used for this purpose. However, existing tools were not designed for large-scale deployments and were mostly validated in controlled settings, considering only one measurement running at a time. In this paper, we argue that current tools, while offering good estimates when used alone, might not work in large-scale systems where several estimations severely interfere with each other. We analyze the properties of the measurement paradigms employed today and discuss their functioning, study their overhead and analyze their interference. Our testbed results show that current techniques are insufficient as they are. Finally, we will discuss and propose some principles that should be taken into account for including available bandwidth measurements in large-scale distributed systems. In this paper, we focus on various experiments conducted to analyze the performance of Transmission Control Protocol (TCP) and Universal Datagram Protocol (UDP) based applications in a IEEE 802.16 deployed network. We analyze the effect of Medium Access Control (MAC) and Physical layer characteristics on the performance of TCP and UDP-based applications. Our key findings are: (i) throughput achieved by TCP-based applications is lower than that of UDP-based applications, (ii) slot utilization of TCP-based applications is lower than that of UDP-based applications and (iii) throughput of TCP-based applications suffers in the presence of UDP-based applications for similar channel states. We also observe that throughput achieved by both TCP and UDP-based applications with Automatic Repeat ReQuest (ARQ) set in system are higher as compared to that of without ARQ. The findings of these experiments can be adopted while designing efficient scheduling schemes for IEEE 802.16-based network, such that higher throughput, utilization and better delay performance can be achieved. TCP performance degrades when end-to-end connections extend over wireless connections — links which are characterized by high bit error rate and intermittent connectivity. Such link characteristics can significantly degrade TCP performance as the TCP sender assumes wireless losses to be congestion losses resulting in unnecessary congestion control actions. Link errors can be reduced by increasing transmission power, code redundancy (FEC) or number of retransmissions (ARQ). But increasing power costs resources, increasing code redundancy reduces available channel bandwidth and increasing persistency increases end-to-end delay. The paper proposes a TCP optimization through proper tuning of power management, FEC and ARQ in wireless environments (WLAN and WWAN). In particular, we conduct analytical and numerical analysis taking into account the three aforementioned factors, and evaluate TCP (and “wireless-aware” TCP) performance under different settings. Our results show that increasing power, redundancy and or retransmission levels always improves TCP performance by reducing link-layer losses. However, such improvements are often associated with cost and arbitrary improvement cannot be realized without paying a lot in return. It is therefore important to consider some kind of net utility function that should be optimized, thus maximizing throughput at the least possible cost.