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HHO (Hard Handover)

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Introduction

HHO or Hard Handover refers to a type of handover that occurs between two base stations in a cellular network. It is an essential feature of mobile communication that allows mobile devices to maintain a seamless connection with the network while traveling between different cells or regions. In HHO, the mobile device disconnects from the serving cell and establishes a new connection with a neighboring cell, which becomes the new serving cell. This process happens instantaneously, and the user doesn't experience any disruption in the network connectivity. In this article, we will discuss the HHO process, its types, advantages, and disadvantages.

HHO Process

The HHO process involves several steps that must be followed to ensure a smooth transition from the old serving cell to the new serving cell. These steps are as follows:

  1. Neighbor Cell Detection: The first step in the HHO process is to detect the neighboring cell's presence. The mobile device continuously monitors the signal strength of neighboring cells and maintains a list of them.
  2. Measurement Report: Once the mobile device detects a neighboring cell, it sends a measurement report to the serving cell containing information about the signal strength and quality of the neighboring cell.
  3. Handover Decision: Based on the measurement report, the serving cell decides whether to initiate the handover process or not. If the neighboring cell's signal strength and quality are better than the serving cell, the serving cell initiates the handover process.
  4. Handover Preparation: Once the handover decision is made, the serving cell starts preparing for the handover by allocating resources in the target cell.
  5. Handover Execution: After the preparation is complete, the serving cell instructs the mobile device to disconnect from the serving cell and establish a connection with the target cell.
  6. Handover Completion: Once the mobile device establishes a connection with the target cell, the handover is complete, and the mobile device can resume communication without any disruption.

Types of HHO

There are two types of HHO based on the handover's direction: Intra-System Hard Handover and Inter-System Hard Handover.

  1. Intra-System Hard Handover: This type of handover occurs within the same system or network. For example, in a GSM network, the handover occurs between two cells belonging to the same BTS (Base Transceiver Station).
  2. Inter-System Hard Handover: This type of handover occurs between two different systems or networks. For example, in a GSM-UMTS network, the handover occurs between a GSM cell and a UMTS cell.

Advantages of HHO

  1. Seamless Connectivity: HHO provides seamless connectivity to mobile devices, which means that users can move between different cells without experiencing any disruption in their communication.
  2. Better Call Quality: HHO ensures that mobile devices are always connected to the cell with the best signal strength and quality. This ensures better call quality and fewer call drops.
  3. Efficient Network Utilization: HHO helps in efficient network utilization by allocating resources to cells based on the traffic load. This helps in improving the network's overall performance and reducing congestion.
  4. Improved Coverage: HHO helps in improving the network's coverage by allowing mobile devices to connect to cells located far away from the serving cell.

Disadvantages of HHO

  1. Complex Network Design: HHO requires a complex network design and infrastructure to ensure seamless connectivity and handover between cells. This increases the network's complexity and maintenance costs.
  2. Delay in Handover: HHO may cause a delay in handover, which may lead to call drops and poor call quality. This can be due to various factors, such as network congestion, interference, or a lack of available resources in the target cell.
  3. Interference and Congestion: HHO can lead to interference and congestion in the network, especially if multiple mobile devices initiate handovers simultaneously. This can lead to reduced network performance and poor call quality.
  4. Increased Power Consumption: HHO requires mobile devices to constantly scan and monitor neighboring cells, which can increase power consumption and reduce battery life.

Conclusion

HHO is an essential feature of mobile communication that ensures seamless connectivity and better call quality. It allows mobile devices to maintain a connection with the network while traveling between different cells or regions. However, HHO also has its disadvantages, such as complex network design, delay in handover, interference, and congestion, and increased power consumption. Network operators need to balance these advantages and disadvantages while designing and maintaining the network to ensure optimal performance and user experience.