Performance analysis of LTE system with different transmission time interval

Long Term Evolution (LTE) system is the major milestone in stepping towards 4G evolution. Further evolution which is named 4.5G (also called as LTE-Advanced Pro) targeting for lower latency and other enhancements is on the way. Many companies put forward that shortening transmission time interval (TTI) length is a possible way to decrease latency in the system in 3GPP meetings. It is known that by shortening the TTI length, throughput gain can be expected. However, how much gain can LTE system obtain is unknown. Moreover, whether there is negative is ambiguous when TTI length is too small. This paper intends to introduce the performance brought by different TTI length in LTE system. The performance is displayed by comparing with legacy TTI length. It presents in different criterions with figures and data, including advantages and disadvantages. This paper also explain why shortening TTI length can affect LTE system's performance.