Throughput Analysis of 3GPP Licensed-Assisted Access Using Multiple Carriers

Due to the urgent demands for wider bandwidth to support continuously blooming wireless applications, deploying Long-Term Evolution Advanced (LTE-A) networks to unlicensed spectrum has been regarded as one of the most crucial remedies to tackle the shortage of available bandwidth on licensed spectrum. This craving consequently drives the development of 3GPP Licensed-Assisted Access (LAA) to sustain both downlink and uplink transmissions of LTE-A (known as LAA networks) on 5 GHz unlicensed spectrum. With vast bandwidth to accommodate a considerable number of bands, simultaneously utilizing multiple bands (carriers) on unlicensed spectrum is of practical interests to enhance data rates, and has been supported in downlink transmissions of LAA. However, to maintain fairness among coexisting users in sharing unlicensed radio resources, transmissions on unlicensed spectrum are restricted by regional regulations such as listen-before-talk (LBT). Particular procedures are also framed by LAA to impose barriers of channel access if an eNB wishes to utilize more than one carriers. Due to the lack of an analytical model to characterize the performance of exploiting multiple carriers, it is a critical challenge for an eNB to determine the optimum number of utilized carriers, which has been the primary concern obstructing the practice of multi-carrier access. In this paper, we consequently provide an analytical model capturing the performance in terms of the number of successful channel accesses (throughput) for an eNB utilizing multiple carriers, to serve the major demand of enhancing data rates. Taking co-channel interference from WiFi and other eNBs into account, the provided model facilitates an eNB to estimate the throughout under given WiFi activity, number of deployed eNBs, and number of utilized carriers. The provided performance analysis thus paves essential foundations for further performance optimization in practical LAA deployment.