Many WiMAX operators today are exploring the opportunities that LTE offers, either as a complementary technology or an alternative to WiMAX. Three developments have compelled this reevaluation of 4G strategies.
First, the growing support for a time division multiplexing (TDD)-version of LTE, TD-LTE, has created a more direct competitor to WiMAX which uses this spectrum. Interest in TD-LTE has spread with many mobile operators attracted by the opportunities for international roaming and cheaper spectrum.
Second, vendors have introduced platforms that support multiple air interfaces through software upgrades, and plan to commercialize multimode devices. The lower cost and complexity of migrating to a new air interface makes it more attractive for WiMAX operators to switch to LTE or to support both 4G technologies.
Third, with a larger market size and commitment from tier-one mobile operators, a powerful LTE ecosystem is building, with a wider choice of devices and competitive equipment prices.
Key factors for WiMAX operators to consider when assessing their options include
LTE will be more attractive to WiMAX operators that target mobile broadband subscribers, giving them access to a wider choice of mobile devices, and facilitating roaming.
WiMAX operators have the flexibility to deploy LTE using TDD or frequency division duplexing (FDD) spectrum bands, while WiMAX equipment is limited to TDD.
WiMAX operators may decide to roll out LTE as a replacement for WiMAX, or as a complementary technology that provides additional capacity and facilitates new services.
WiMAX operators may wait until the LTE ecosystem is more developed to reap the full benefits of transition and minimize its costs.
Equally important for operators to consider is service continuity within the core network and full service portability.
The transition to LTE must be transparent to subscribers. Service plan features, billing, application and bandwidth management, and provisioning must be consistent as subscribers move from WiMAX to LTE. This is even more important if WiMAX and LTE coexist, because subscribers will frequently switch among interfaces and should be able to do so without noticing any change in their service.
For these reasons, a smooth transition of the control plane in the IP core, including subscriber data management, policy control, and service control is crucial.
Operators have different transition options as shown in the table. For a swap of WiMAX for LTE, a software upgrade of common modules will suffice. If the two networks need to coexist, two core networks have to be established, but some elements can be shared.
The similarities between WiMAX and LTE, the streamlined upgrade process, and the pressing need to response to steep mobile data traffic growth have made it possible for a new breed of operator to emerge — the 4G operator.
David Sharpley, senior vice president, Bridgewater Systems