hi, need to learn about lte handover algorithm using Ant Colony Algorithm.

handover lte matlab optimization source code

With Long Term Evolution (LTE), the pros most definitely outweigh the cons. This new and improved network will provide faster speeds and handle the ever-increasing data demands. Note every user, however, is ready for LTE. Both 3G and 2G networks are still in wide use and LTE must find a way to work with both, dealing with the handover that may arise.

There are many ways to handle this LTE handover. According to Artiza Networks, handover procedure, when working correctly, should reduce the interruption time, less than the circuit-switched handover in 2G networks, and it is an important function for LTE eNB. There are multiple LTE handover procedures to be tested, shown below. LTE eNB must implement handover procedure inside E-UTRAN (Inter eNB/Intra eNB) and also between legacy Radio Access Technologies (RAT) like UMTS.

Introduction

Handover (HO) is key procedure for ensuring that users can move freely within a network being connected to high quality services [1]. In currently deployed mobile networks, handover optimization is performed manually over a long time period - days or weeks. This approach is both time consuming and can not be carried out as often as needed. By introducing an online self-optimising algorithm that can tune the parameters of the HO process, we aim at improving overall network performance and user QoS. The main goals are reducing the number of HOs that are initiated but not carried out until completion (HO failures), repeated back and forth HOs between two base stations (’ping-pong’ HOs) and dropped calls.

One of the most important directions of LTE expertise evolution is comprehension of Self-Organizing Network (SON) functionality [2]. Every wireless telecom service provider needs infrastructure that is self-configuring, self-operating and self-optimizing. Ideal infrastructure deploys quickly without any special expertise, automatically discovers the neighbors, automatically reconfigures around network failures and automatically optimizes radio parameters. In addition, backhaul and interconnect should be automatically configured and QoS should be self-established and autonomously optimized. These capabilities, along with many others, are the vision of the SON.

SON is defined as a set of use cases that covers the entire network lifecycle: planning, deployment, operation and optimization. Hence, SON is designed to be a multi-vendor solution. The key SON subjects are network planning, network deployment and network optimization. The goal of SON at the stage of network planning is to eliminate as much pre-planning of network configuration as possible. SON does allow pre-planned network configuration, but it strongly encourages that as much of network configuration as possible should be generated/discovered automatically. The goal of SON at the stage of network deployment is to radically decrease deployment time and procedures, especially in the deployment of eNBs. The goal of SON at the stage of network optimization is to maintain the desired performance level over the life of the network as new equipment is deployed, usage patterns change, etc. In particular SON optimization should provide automatic handoff optimization, including monitoring KPIs (key performance indicators) to optimize handoff by iteratively adjusting target C/I (carrier-to-interference) and RSSI (received-signal strength indication).

Self-optimization of future radio access networks is one of the main topics for MERA research group. MERA has developed an LTE system-level Matlab-based simulator. It allows evaluating and optimizing the system performance. This paper describes the handover parameter optimization problem for LTE.

2. Handover procedure

There are two types of handover procedure in LTE for UEs in active mode:

the S1-handover procedure;
the X2-handover procedure.
The S1-handover procedure is performed between two eNBs without the X2 interface. The X2 handover is used when direct connectivity between source and target eNBs exists. The X2 handover is quicker. The message chart of the X2 handover procedure is reported in Figure 1 [1]. During the handover, the Transmission Control Protocol (TCP) endpoints must be moved from the Source eNB to the Target eNB. The Source eNB collects the UE measurements of the page link quality and assists in the function control of the UE’s handover. As a next step, source eNB makes a decision based on the measurement reports and RRM information to hand off the UE and it issues a handover request message to the Target eNB. After that, admission control may be performed by the Target eNB according to the received quality of service information. The Target eNB prepares the handover and sends the handover request acknowledgement to the Source eNB. Such a message may also include information about Radio/Transport Network Layer (RNL/TNL) for the forwarding tunnels. When handover request acknowledgement is received, data forwarding from the Source eNB to the Target eNB through the router may be initiated. The Source eNB generates the handover command (RRC message) towards the UE. Then, the UE performs synchronization to Target eNB and accesses the target cell. Then it sends a handover message to indicate that the handover procedure is completed. The Target eNB can now start sending data to the UE and at the same time send a path switch message to the server MME to inform that the UE has changed the cell.

Handover can be described as a very precise flow of events and some might argue that there is little if anything to be improved in it. In our approach we are looking not at modifying this flow but rather at making the parameter settings that control it flexible and modifying them accordingly. The main challenges faced by such an algorithm is finding a perfect balance between the control parameters of the HO process and ensuring that the network is in a stable operating point for a long time.