Let’s talk something about TDD LTE and FDD LTE’s Advantages / disadvantages of for cellular communications.
As we know, the LTE mainly covers two types, which are TDD and FDD. There are a number of the advantages and disadvantages of TDD and FDD that are of particular interest to mobile or cellular telecommunications operators. These are naturally reflected into LTE.
| COMPARISON OF TDD LTE AND FDD LTE DUPLEX FORMATS | ||
| PARAMETER | TDD LTE | FDD LTE |
| Channel reciprocity | Channel propagation is the same in both directions which enables transmit and receive to use on set of parameters | Channel characteristics different in both directions as a result of the use of different frequencies |
| Paired spectrum | Does not require paired spectrum as both transmit and receive occur on the same channel | Requires paired spectrum with sufficient frequency separation to allow simultaneous transmission and reception |
| Hardware cost | Lower cost as no diplexer is needed to isolate the transmitter and receiver. As cost of the UEs is of major importance because of the vast numbers that are produced, this is a key aspect. | Diplexer is needed and cost is higher. |
| UL / DL asymmetry | It is possible to dynamically change the UL and DL capacity ratio to match demand | UL / DL capacity determined by frequency allocation set out by the regulatory authorities. It is therefore not possible to make dynamic changes to match capacity. Regulatory changes would normally be required and capacity is normally allocated so that it is the same in either direction. |
| Guard period / guard band | Guard period required to ensure uplink and downlink transmissions do not clash. Large guard period will limit capacity. Larger guard period normally required if distances are increased to accommodate larger propagation times. | Guard band required to provide sufficient isolation between uplink and downlink. Large guard band does not impact capacity. |
| Cross slot interference | Base stations need to be synchronised with respect to the uplink and downlink transmission times. If neighbouring base stations use different uplink and downlink assignments and share the same channel, then interference may occur between cells. | Not applicable |
| Discontinuous transmission | Discontinuous transmission is required to allow both uplink and downlink transmissions. This can degrade the performance of the RF power amplifier in the transmitter. | Continuous transmission is required. |
