Latency Reduction Techniques in Modern Mobile Networks

Latency is referred to the time taken between making a request to and receiving a response from a network. It is measured in milliseconds (ms) as it is a time based value. High latency is a large delay between this sending and receiving of responses and is caused by a number of factors. In today's high speed world low latency is a necessity to keep users using a network or service for example a user may leave a website if the load time is less than 3 seconds hence techniques must be employed to reduce latency as much as possible if we are to achieve real time communication, streaming and gaming in mobile networks

Causes of Latency

1. Propagation Delay - This refers to the amount of time taken to send data from a sender to a receiver and is caused by the physical distance between the two devices and the speed of the transmission medium. A large distance between a user’s mobile device and a data center increased latency due to the amount of time required for data to reach one point from another.

2. Transmission Delay - This refers to the amount of time taken to transmit all the bits of a packet to the transmission medium by a network and is dependent on the size of the packet being transmitted and bandwidth of the network. Low bandwidth and large data packets contribute to high latency as more time is needed to transmit all of the bits of the data.

3. Queuing Delay - This is when data packets wait at various network nodes such as routers and switches for preceding packets to be sent before they can be processed and forwarded. This delay occurs mainly when there’s high network usage or in congested areas with limited bandwidth.

4. Processing Delay - This refers to the time taken by network nodes such as routers, switches and base stations to examine, validate and route data packets, each node in the network performs processing functions which can introduce delays leading to increased latency especially if the node is using old hardware or software or if extra steps are needed on the packet such as encryption.

5. Protocol Overhead - This delay occurs from communication protocols that manage data transfer, security and reliability such as TCP/IP. For example TCP requires a three-way handshake to establish a connection, additionally protocols that require retransmission or acknowledgements can also introduce delays especially if packet loss occurs. TCP also does this.

6. Network Congestion - This is when too many users try to access a network simultaneously, exceeding the available bandwidth leading to bottlenecks as packets compete for limited resources causing queuing and transmission delays. This mainly occurs in high population areas or during peak usage times. 

Latency Reduction Techniques

1. Network Slicing in 5G - This refers to the dividing of the physical network into multiple virtual networks each with their own quality of service profile QOS. This enables different applications to operate on dedicated network segments optimized for their unique requirements. For example applications that require low latency such as online gaming or remote survey can have their own network slice with guaranteed resources avoiding contention with other data heavy but non-urgent applications.

2. Dual Connectivity - Allows mobile devices to connect to two base stations e.g. one for 4G and one for 5G or both for 5G or 4G. This allows for redundancy and improved bandwidth such that if one network is congested data can flow to the other, effectively balancing and reducing delay.

3. Edge Computing - Edge computing brings data processing closer to the user by placing servers at the edge of the network, near cell towers or within base stations. This effectively reduces the round trip time as the data doesn’t have to travel to a centralized server for processing, for example if a user accesses a service hosted on the edge the service responds almost instantly due to the small distance to travel effectively reducing latency.

4. Small Cell Deployment - Small cells are low-power radio access nodes usually placed closer to the users in dense urban or indoor environments and they supplement the traditional macro cell towers. These small cell towers reduce the amount of distance required to travel by the data to the base station effectively reducing queuing delays and improving signal quality especially in densely populated areas.

5. Network Protocol Optimization - Protocols such as Quick UDP internet Connections (QUIC) and HTTP/2, HTTP/3 are all optimized for faster data transfer. QUIC uses UDP instead of TCP for data transfer eliminating the handshake step carried out by TCP. These protocols reduce delays with connection setup and retransmission effectively reducing round trip time thus reducing latency as applications are able to get a response.

6. Carrier Aggregation - Carrier aggregation allows devices to use multiple frequency bands at once to increase bandwidth. This is common in 4G LTE and is used extensively in 5G. By combining frequency bands we are able to improve data throughput allowing devices to send and receive data more quickly reducing delays and improving bandwidth.

Conclusion

By implementing these techniques mobile networks are able to reduce latency substantially allowing for robust, reliable, high speed connections which are required for modern real time applications such as gaming, IoT, AR-VR and autonomous systems.