Interoperability of GPON and WiMAX for network capacity enhancement and resilience

Milos Milosavljevic, Yuval Shachaf, Pandelis Kourtessis, John M. Senior
2009 Journal of Optical Networking  
The interoperability of standard WiMAX and GPON is shown to overcome the wireless spectrum congestion and provide resilience for GPON through the use of overlapping radio cells. The application of centralised control in the optical line terminal (OLT) and time division multiplexing for upstream transmission enables efficient dynamic bandwidth allocation for wireless users on a single wavelength as well as minimised optical beat interference at the optical receiver. The viability of
more » ... transmission of multiple un-coded IEEE802.16d channels by means of a single radio frequency (RF) subcarrier at transmission rates of 50 Mbits/s and 15 Mbits/s downstream and upstream respectively for distances of up to 21 km of integrated GPON and WiMAX micro-cell links is demonstrated. OCIS codes: 060.4250, 060.4510. Introduction The emergence of new bandwidth-intensive applications articulated by distance learning, online gaming and movie delivery by means of high-definition video are providing the impetus for upgrading the access network infrastructure to establish broadband pipes at close proximity to the user. Passive optical networks (PONs) offer more opportunities to communicate these services than ever before, providing for the necessary connection speeds per user of 100 Mbits/s [1]. Although PONs can provide high-bandwidth 2 and quality of service (QoS), the deployment cost in particular of running fibre from street cabinets to the home is currently relatively high [2] . Beyond that, in a typical tree topology, such as the Gigabit-PON (GPON) [3], redundancy is required in case of fibre failure between a distribution node and an optical network unit (ONU). The various possible methods on providing redundancy are summarised in [4], however, all suggest that dual-fibre should be used that leads to high investment costs for operators. By contrast, wireless access networks require less infrastructure deployment and can provide ubiquitous access connections to end users. In addition, broadband wireless technologies, such as WiMAX [5] , are gradually developing to expand their bandwidth capacity, coverage and QoS, to complement their established mobility. Hence, a viable access solution for the future could be obtained by leveraging the advantages of both technologies combined on an integrated architectural platform [6] . In order to minimise network installation and maintenance costs, it would be desirable to make radio antenna units as simple as possible by shifting expensive devices and signal processing at the centralised head-end through the use of radio-over-fibre (RoF). Additionally, to the clear cost saving in hardware, such infrastructure would benefit from a flat control plane and seamless convergence by which signalling and control messages are directly exchanged between the optical line terminal (OLT) and end users [7, 8] . An original radio-over-fibre access network architecture is described and investigated to provide WiMAX functionality features over deployed GPON platforms, primarily aiming to enable redundancy in GPON through wireless connections as well as to improve wireless spectrum congestion and thus increase the WiMAX network capacity. This has been achieved by introducing, for the first time, the concept of overlapping radio cells centrally controlled by the OLT. In comparison, published work in converged optical-wireless networks with respect to network connectivity and fault-tolerance [7] is based on interconnected wireless routers distributed in the locality of ONU base station gateways. Since the wireless routers are configured on a mesh topology user data would need to travel over multiple hops in the field on route to corresponding ONUs imposing extensive resource allocation and complicated routing algorithms to achieve resilience [9] . In contrast, each ONU in the proposed architecture simply serves as a wireless signal relay, providing direct connectivity to wireless users in agreement with typical cell
doi:10.1364/jon.8.000285 fatcat:ney7zxxtkfe7lkuajd2ovukp5e