Mobility and Radio Resource Management in Future Aeronautical Mobile Networks

Kurzfassung

The aviation community is currently working on the standardization of data communication systems for the future air traffic management. The standardization effort has two main streams, namely, standardization of future radio access technologies and standardization of a future IPv6 based aeronautical telecommunications network (ATN/IPS). In this thesis, different handover and radio resource management algorithms are analyzed for the L-band digital aeronautical communications system option 1 (LDACS1) which is integrated with realistic IPv6-based network layer functionality. In the first part of this work, handover performance of network mobility (NEMO) is investigated and different cross-layer approaches are proposed in order to improve handover latency and signalling overhead. These improvements mainly use media independent handover functionality proposed by the IEEE 802.21 standard and are important due to the following reasons: • One of the main system requirements of LDACS is to deliver certain ATS messages in a timely manner (i.e. low latency) with minimum service disruption time (i.e. high service availability). • In parallel, some new future services like VoIP and transmission of sensor data for the aircraft health management also require “real-time” and “nearreal- time” transmission of certain information with low latency and high availability. • According to STATFOR statistics, number of flights in Europe will be around 17 million in 2030 annually, which is 1.8 times more than in 2009. Since LDACS is planned for the time frame of 2020-2030, it should be capable of handling the data traffic demands of the future ATM. From this perspective, reducing the signalling overhead in the wireless network should be one of the design criterion for the air-ground part of the ATN/IPS. With our proposals, total handover latency (i.e. layer 2 and layer 3) is reduced to around 0.4 s and signalling overhead due to router advertisement messages is reduced to around 0.1 kbit=s. In the second part, the effect of handover delay on transmission control protocol (TCP) performance is analyzed. We first provide an analysis on selecting right TCP parameters in order to use it over LDACS1 effectively. This is important since TCP is adopted by ATN/IPS as the main transmission control protocol for connectionoriented services at the transport layer. Later on, we propose a new handover optimization technique for on-going TCP sessions during handover since some TCP sessions take long time which may experience an handover event and are affected negatively due to handover event. This new technique uses home agent buffering method and integrates it with the LDACS1 handover procedure. With the help of this method, total transmission completion time of a session is reduced by at least 10% for a download of 110 kByte of information. In the third part, different radio resource management (RRM) algorithms are analyzed for the LDACS1 since the resources should be distributed evenly among different users. This is not only important from fairness perspective but also from "expiration time" and "latency" requirements of ATS/AOS messages. Here, we analyzed different RRM algorithms in terms of bandwidth and end-to-end delay fairness. We also provide a new modified deficit round robin algorithm which could be used for both links (i.e. forward and return link) and satisfy almost perfect fairness among different number of users. In the last part, different NEMO route optimization techniques (RO) are analyzed due to triangular routing problem of NEMO. With the help of NEMO RO, packets follow shorter paths between the end nodes so that the measured end-to-end delay and path length are reduced. Most of these NEMO RO methods are published as Internet Engineering Task Force drafts. Among those proposals, we have realized that some of them require mobility related functionalities to the end nodes and some others do not. In addition, some proposals try to solve nested NEMO problem without working on the main route optimization problem. In addition, since most of those protocol are published as IETF draft, some protocols lack of protocol design and maturity in terms of implementation. Considering these issues, we mainly analyze infra-structure based NEMO RO techniques; namely global home agent to home agent (Global HAHA) and correspondent router (CR) protocols from ATN/IPS perspective in the first part. Later on, we propose two new approaches for the global HAHA protocol in order to decrease end-to-end delay and mobility signalling overhead.