Low latency user plane radio links are substantially enhanced by 3GPP's NR and E-UTRAN radio technologies in Release 15. Mobility remains one of the key differentiators between 3GPP's technologies and other systems (e.g. systems that use unlicensed radio, or fixed networks). Hence it is important to network operators that mobility is effectively supported for the enhanced, low latency radio features.
As the Release 15 RAN enhancements are targeted at around 1 ms one-way radio interface latencies, this TR looks at architectural enhancements and solutions for networks where the transmission latency between the radio base station site and SGi can be around 0.1 ms to 1 ms latency (c.f. 20-200km of speed of light delay in optic fibre).
This Technical Report investigates the enhancement of EPC for low latency communication including device mobility, using the CUPS architecture (TS 23.214
) and by identifying solutions based on EPC functionality (TS 23.401
) in the following area:
improvements to enable low latency following UE mobility and, possibly, following the activation of a service requiring low latency.
The aim is to retain the single SGW-C per UE concept but utilise SGW-C's "independent SGW-U per PDN connection" concept and expect to base on a "make before break" PDN connection mobility concept (with UE IP address change). To deliver low latency it is anticipated (but not mandated) that most solutions will use a combined S/PGW(-U).Anticipated investigations include:
whether to initiate "make before break" from e.g. MME or PCRF;
the need for e.g. PGW-C to PCRF interface extensions to support "make before break" PDN connection mobility (and if needed to support this, e.g. MME-SGW-PGW interface extensions).
Possible intermediate versions of the solutions may be maintained in this Technical Report.