Hiroyuki Uzawa

Effective utilization of unallocated intervals in TDD-based fronthaul employing TDM-PON

A time-division-multiplexing passive optical network (TDM-PON) accommodating a time-division duplex (TDD)-based mobile fronthaul (MFH) contributes to the realization of a low-cost network. However, there are two issues with the TDM-PON. The first is the limited number of optical network units (ONUs) that can be accommodated because the statistical multiplexing effect is weaker than with the accommodation of a conventional MFH. The other issue is the discovery process for registering new ONUs. While operating the discovery process, the signals of the registered ONUs cannot be forwarded in the optical link, and a huge latency is added to the registered ONUs. We have proposed a technique for the effective utilization of unallocated intervals, which certainly occur in optical links. Secondary service signals are forwarded in the unallocated intervals to increase the number of ONUs. The discovery process also operates in the unallocated intervals to avoid any latency increase. In this paper, we report evaluation results obtained using the numerical simulations.

TDM-PON for Accommodating TDD-Based Fronthaul and Secondary Services

A time division multiplexing-passive optical network (TDM-PON) has been attracting attention with a view to realizing the cost-effective mobile fronthaul (MFH) of a mobile base station (BS). A cost-effective MFH is needed because a lot of BSs will be densely deployed in fifth generation mobile networks (5G). A TDM-PON is capable of reducing the network cost as the number of subscribers increases. However, the number of remote radio heads that can be accommodated in a TDM-PON is limited since a 5G MFH has a throughput of more than 1 Gbps. The accommodation of not only the MFH but also multiple services will enable us to construct a more cost-effective network that will in turn achieve cost-effective 5G MFH. Therefore, we propose the accommodation of the fronthaul and secondary services in a TDM-PON. Our proposed TDM-PON allows us to increase the number of accommodated ONUs. We use a traffic monitor to capture the MFH signal and then estimate the unallocated interval in the PON domain by using the characteristics of the MFH signal. The signals of the secondary services are inserted in the unallocated interval of the MFH signal. We estimate the unallocated interval by using this characteristic. In this paper, we report experimental and the theoretical results for our proposed technique obtained with a 10 Gigabit-Ethernet PON prototype. Moreover, we also discuss the variation in throughput when we increase the number of ONUs.