Method to modify the frequency hopping scheme by extending the validity of the reference signals
The present invention increases the interference diversity in systems with the frame structure described above by using frequency hopping sequences that are selected considering characteristics of the channel relating to how the channel varies. According to a first embodiment, the channel characteristics relate to channel coherence time and according to a second embodiment, the channel characteristics relate to channel coherence bandwidth. For channels with long coherence times, the transmission hops back and forth several times during a TTI on the different available frequencies. For channels with wide coherence bandwidths, hopping may be performed between the frequency used by the reference signals and its neighbor frequencies. For channels with both long coherence times and wide coherence bandwidths, a combination may be used.
1. A method for a radio access network using frequency hopping schemes based on channel parameters comprising time and frequency parameters, the radio access network is configured for transmission of data symbols and reference symbols in different bursts and wherein the number of data symbol bursts exceeds the number reference symbol bursts, the method is characterised by the steps of:
identifying at least one channel parameter and its associated value over which the channel is being substantially constant, and
modifying the used frequency hopping scheme by extending the range of the validity of the reference symbol bursts in a dimension of the identified channel parameter, wherein the data symbols are transmitted within said extended validity to increase interference diversity.
2. The method according to claim 1 , wherein the at least one identified channel parameter is a time parameter implying a long channel coherence time.
3. The method according to claim 2 , wherein one slot comprises a plurality of data symbol bursts and one reference symbol burst, and in at least one previous slot, the one reference symbol burst is valid.
4. The method according to claim 2 , wherein one slot comprises a plurality of data symbol bursts and one reference symbol burst, and in at least one subsequent slot, the one reference symbol burst is valid.
5. The method according to claim 1 , wherein the at least one identified channel parameter is a frequency parameter implying a wide channel coherence bandwidth.
6. The method according to claim 5 , wherein the reference symbol bursts are valid on at least one neighboring frequency of the reference symbol bursts.
7. The method according to claim 1 , wherein the at least one identified channel parameter is a time parameter implying a long channel coherence time and a frequency parameter implying a wide channel coherence bandwidth.
8. The method according to claim 7 , wherein one slot comprises a plurality of data signal bursts and one reference symbol burst, the one reference signal burst is valid in at least one previous or subsequent slot, and the one reference symbol burst is valid on at least one neighboring frequency of the reference symbol burst.
9. An arrangement for a radio access network using frequency hopping schemes based on channel parameters comprising time and frequency parameters, the radio access network is configured for transmission of data symbols and reference symbols in different bursts and wherein the number of data symbol bursts exceeds the number reference symbol bursts, the arrangement is characterised by:
means for identifying at least one channel parameter and its associated value over which the channel is being substantially constant, and
means for modifying the used frequency hopping scheme by extending the range of the validity of the reference symbol bursts in a dimension of the identified channel parameter,
wherein the data symbols are transmitted within said extended validity to increase interference diversity.
10. The arrangement according to claim 9 , wherein the at least one identified channel parameter is a time parameter implying a long channel coherence time.
11. The arrangement according to claim 10 , wherein one slot comprises a plurality of data symbol bursts and one reference symbol burst, and in at least one previous slot the one reference symbol burst is valid.
12. The arrangement according to claim 10 , wherein one slot comprises a plurality of data symbol bursts and one reference symbol burst, and in at least one subsequent slot, the one reference symbol burst is valid.
13. The arrangement according to claim 9 , wherein the at least one identified channel parameter is a frequency parameter implying a wide channel coherence bandwidth.
14. The arrangement according to claim 13 , wherein the reference symbol bursts are valid on at least one neighboring frequency of the reference symbol bursts.
15. The arrangement according to claim 9 , wherein the at least one identified channel parameter is a time parameter implying a long channel coherence time and a frequency parameter implying a wide channel coherence bandwidth.
16. The arrangement according to claim 15 , wherein one slot comprises a plurality of data signal bursts and one reference symbol burst, the one reference signal burst is valid in at least one previous or subsequent slot, and the one reference symbol burst is valid on at least one neighboring frequency of the reference symbol burst.
17. The arrangement according to claim 9 , wherein the arrangement is configured to be implemented in association with a transmitter.
18. The arrangement according to claim 9 , wherein the arrangement is configured to be implemented in association with a receiver.