LTE intra frequency vs inter frequency question
His main question was about mobility. Mobility in LTE can be quite tricky. The main point of his question was about the frequency band size. In LTE there is a scalable OFDM channel. The bandwidth can vary from 1.4 MHz to 20 MHz. There are also a number of frequency bands that are going to be used for LTE (the new 700 MHz as well as the old PCS and Cellular bands).
The question basically was can a mobile move between frequency bands and the answer is absolutely yes. The second part of the question regarded movement between different sizes of bands. The best way to approach this question is to define two terms. The two terms are intra-frequency and inter-frequency mobility. We are use to these terms in other technologies (i.e. GSM and UMTS), but LTE puts a new spin on things. Intra-frequency mobility is when a mobile moves between two cells and both cells have the same frequencies (I know, not the most profound statement). If there is a change in the center frequency this is now called inter-frequency mobility. In LTE both intra-frequency and inter-frequency mobility are supported. (5/4/10 Note - I has come to my attention that if the bandwidth changes, but the center frequency does not change it is still a intra-frequency handover.)
For example, let's say that an operator has in one city a 10 MHz block in the 850 MHz band that they are using for LTE. In a city that is only a few miles away this same operator has only 5 MHz available in the 850 MHz band. When a subscriber drives from city A to city B the size of the frequency band is changing (as will probably the DC carrier) and the mobile will have to do inter-frequency mobility measurements to provide information on the new cells signal strength.
The reason this is an important discussion is that when the mobile does intra-frequency measurements the network does not need to allow any time to do the measurements. The mobile can just do them whenever they want to. For inter-frequency measurements the mobile must be given time to stop listening to its current cell and listen to a new cell to take the measurements. That increases the level of complexity and the amount of work the mobile will need to do.
The question basically was can a mobile move between frequency bands and the answer is absolutely yes. The second part of the question regarded movement between different sizes of bands. The best way to approach this question is to define two terms. The two terms are intra-frequency and inter-frequency mobility. We are use to these terms in other technologies (i.e. GSM and UMTS), but LTE puts a new spin on things. Intra-frequency mobility is when a mobile moves between two cells and both cells have the same frequencies (I know, not the most profound statement). If there is a change in the center frequency this is now called inter-frequency mobility. In LTE both intra-frequency and inter-frequency mobility are supported. (5/4/10 Note - I has come to my attention that if the bandwidth changes, but the center frequency does not change it is still a intra-frequency handover.)
For example, let's say that an operator has in one city a 10 MHz block in the 850 MHz band that they are using for LTE. In a city that is only a few miles away this same operator has only 5 MHz available in the 850 MHz band. When a subscriber drives from city A to city B the size of the frequency band is changing (as will probably the DC carrier) and the mobile will have to do inter-frequency mobility measurements to provide information on the new cells signal strength.
The reason this is an important discussion is that when the mobile does intra-frequency measurements the network does not need to allow any time to do the measurements. The mobile can just do them whenever they want to. For inter-frequency measurements the mobile must be given time to stop listening to its current cell and listen to a new cell to take the measurements. That increases the level of complexity and the amount of work the mobile will need to do.
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