Due to the evolution of mobile technology and the emergence of terminals like smart phones, Internet based applications mostly accessed over the Transmission Control Protocol (TCP) have become dominant on mobile platforms. However, since the TCP flow control mechanisms were designed for wired environments, short-term degradations on the air interface of radio access systems may lead to unnecessary performance drops. TCP freeze is a possible solution to improve such situations by triggering the persist mode of the TCP sender, preventing TCP timeouts and rate reductions during poor radio conditions. This paper investigates a network element based implementation of the TCP freeze mechanism, which has the advantage that it can accurately follow the radio conditions of the User Equipments (UE) while being completely transparent to the TCP sender and receiver. The possible performance gain of the solution was investigated by simulating a network with coverage holes. Results indicate that the network side freeze can considerably reduce the time the TCP connections spend in outage and thus it can increase the responsivity and data throughput provided by the system.
No abstract
Evolved HSPA is a distributed, packet based radio access system that provides high user data rate and low latency. In our contribution the performance of streaming applications over Evolved HSPA is analyzed in realistic network scenarios. The simulation results indicate that in certain scenarios the adaptation latency experienced in case of applying 3GPP PSS Release 8compliant streaming adaptation is excessively high, causing stream degradation and thus contributing to an end user experience of lower quality. Possible ways of mitigation are briefly outlined.
The high end-user data rates provided by HSDPA makes it a realistic alternative of wired Internet access. New 3GPP releases and the migration to packet based transport are further improving the capabilities of HSDPA. As a result, mobile data traffic is continuously increasing, various packet based services and applications with different QoS requirements are now accessible through HSDPA systems. This evolution requires efficient radio and transport QoS solutions and traffic differentiation methods. The HSDPA QoS framework specified by 3GPP and the air interface packet scheduling disciplines such as PF-RAD enforce the QoS and differentiation per connection level. In contrast, transport QoS architectures such as DiffServ are class based; differentiation is possible only per traffic aggregate level. The different approaches might result in inefficient system operation where the end-to-end QoS can be offered only by reducing the resource usage. This paper proposes a solution that aligns the operation of the transport and radio QoS mechanisms by continuously reconfiguring the transport schedulers. The performance of the proposed solution is investigated with simulations.
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