Avoiding transmitter collision sessions in femtocells arrays
Control unit within a femtocell base station is arranged to detect a transmission collision situation and resolves it by adjusting the timing of the transmission signal and consequently the frame position gradually over time. The adjustment (or shift) is performed in a slow enough rate such that the User Equipments currently connected (camped) to the femtocell base station remain connected. Additionally, a method is also provided. The method comprises: detecting neighboring base stations; detecting frame boundaries of the transmitting signal of each detected neighboring base station; calculating optimal transmit position; setting transmit position to calculated optimal transmit position; and maintaining optimal transmit position by gradually adjusting transmit position over time. In case, detecting neighboring base stations is not possible, the method comprises: detecting absolute time drifting in view of an absolute accurate time reference and maintaining constant absolute transmit position by gradually adjusting transmit position over time.
1. A femtocell base station, comprising:
a femtocell base station control unit configured to generate a transmission signal exhibiting a plurality of periodic frames, wherein each frame exhibits frame boundaries and an active transmit signal within the frame boundaries, and wherein the active transmit signal includes a temporal transmit position being a start point of the transmission signal; and
a collisions avoidance module configured to:
detect neighboring base stations;
detect frame boundaries of a signal transmitted by each of the detected neighboring base stations when neighboring base stations are detected;
select the temporal transmit position such that a likelihood of collisions between transmit signals is minimized when neighboring base stations are detected;
select the temporal transmit position to be a current transmit position added to a predefined number of chips when no neighboring base station are detected for a predefined period of time;
set a transmit position to the selected temporal transmit position; and
gradually adjust the selected temporal transmit position over time such that the likelihood of collisions between transmit signals remains minimized.
2. The femtocell base station according to claim 1 , wherein the collisions avoidance module is configured to detect frame boundaries by instructing a connected user equipment to measure a time difference between two cells.
3. The femtocell base station according to claim 1 , wherein the selected temporal transmit position is selected such that a distance between the selected temporal transmit position and transmit positions of the neighboring base stations are maximized.
4. The femtocell base station according to claim 1 , wherein the collisions avoidance module is configured to minimize the likelihood of collisions between transmit signals by using at least one of: a GPS receiver, NTP, PTP, a timing protocol over IP, an internal reference clock inside a femtocell, or a central clock coupled to a macrocell base station.
5. The femtocell base station according to claim 1 , wherein the femtocell base station control unit is further configured to communicate with a mobile operator network, and wherein the mobile operator network is operable within at least one of the following cellular communication standards: UMTS, HSPA, GSM, CDMA-2000, TD-SCDMA, LTE or WiMAX.
6. The femtocell base station of claim 1 , wherein gradually adjusting the selected temporal transmit position over time includes adjusting the selected temporal transmit position at a rate such that user equipment connected to the femtocell base station remains connected.
7. The femtocell base station of claim 1 , wherein gradually adjusting the selected temporal transmit position over time includes adjusting the selected temporal transmit position at a rate of less than 25 chips in a 5 second time period.
8. A method of avoiding collisions between transmit signals of neighboring femtocell base stations, wherein each femtocell base station is configured to generate a transmission signal exhibiting periodic frames, wherein each frame exhibits frame boundaries and an active transmit signal within the frame boundaries, and wherein the active transmit signal includes a temporal transmit position being a start point of the transmit signal, the method comprising:
detecting neighboring base stations;
detecting frame boundaries of the transmit signals of each detected neighboring base station;
selecting the temporal transmit position such that a likelihood of collisions between transmit signals is minimized in view of the detected frame boundaries when neighboring base stations are detected;
selecting the temporal transmit position to be a current transmit position added to a predefined number of chips when no neighboring base stations are detected for a predefined period of time;
setting a temporal transmit position to the selected temporal transmit position; and
gradually adjusting the selected temporal transmit position over time such the likelihood of collisions between transmit signals remains minimized.
9. The method of claim 8 , wherein detecting the frame boundaries is achieved by instructing a connected user equipment to measure a time difference between two cells.
10. The method of claim 8 , wherein selecting the temporal transmit position is achieved by selecting the transmit position that maximizes a distance between the transmit position and the transmit positions of the neighboring base stations.
11. The method of claim 8 , wherein selecting the temporal transmit position such that the likelihood of collisions between transmit signals is minimized is achieved using at least one of: a GPS receiver, NTP, PTP, a timing protocol over IP, an internal reference clock inside a femtocell, or a central clock coupled to a macrocell base station.
12. The method of claim 8 wherein the method is operable within at least with one of the following communication standards: UMTS, HSPA GSM, CDMA-2000, TD-SCDMA, LTE or WiMAX.
13. The method of claim 8 , wherein gradually adjusting the selected temporal transmit position over time includes adjusting the selected temporal transmit position at a rate such that user equipment connected to the femtocel base station remains connected.
14. A cellular communication network, comprising a plurality of macrocell base stations and femtocell base stations, comprising:
a femtocell base station control unit, incorporated within at least one of the plurality of femtocell base stations, configured to generate a transmission signal exhibiting periodic frames, wherein each frame exhibits frame boundaries and an active transmit signal within the frame boundaries, and wherein the active transmit signal includes a temporal transmit position being a start point of the transmit signal; and
a collisions avoidance module configured to:
detect neighboring base stations;
detect frame boundaries of a signal transmitted by each detected neighboring base station;
select the temporal transmit position such that a likelihood of collisions between transmit signals is minimized when neighboring base stations are detected;
select the temporal transmit position to be a current transmit position added to a predefined number of chips when no neighboring base stations are detected for a predefined period of time;
set a transmit position to the selected temporal transmit position; and
gradually adjust the selected temporal transmit position over time such that the likelihood of collisions between transmit signals remains minimized.
15. The cellular communication network according to claim 14 , wherein the collisions avoidance module is configured to detect frame boundaries by instructing a connected user equipment to measure a time difference between two cells.
16. The cellular communication network according to claim 14 , wherein the selected temporal transmit position is selected such that a distance between the selected transmit position and the transmit positions of the neighboring base stations is maximized.
17. The cellular communication network according to claim 14 , wherein the collisions avoidance module is configured to minimize the likelihood of collisions between transmit signals by using at least one of: a GPS receiver, NTP or PTP, a timing protocol over IP, an internal reference clock inside a femtocell, or a central clock coupled to a macrocell base station.
18. The cellular communication network according to claim 14 , wherein the femtocell base station control unit is further configured to communicate with a mobile operator network, and wherein the mobile operator network is operable within at least one of the following cellular communication standards: UMTS, HSPA, GSM, CDMA-2000, TD-SCDMA, LTE or WiMAX.
19. The cellular communication network according to claim 14 , wherein setting the transmit position is performed at a rate such that user equipment currently connected to at least one of the plurality of femtocell base stations remains connected.
20. The cellular communication network of claim 14 wherein gradually adjusting the selected temporal transmit position over time includes adjusting the selected temporal transmit position at a rate such that user equipment connected to the femtocell base station remains connected.