Synchronized network transmission

• US 8,817,736 B2
• Filed: 10/28/2012
• Issued: 08/26/2014
• Est. Priority Date: 10/29/2011
• Status: Active Grant

• Current Assignee: Comcast Cable Communications LLC (Comcast Corporation)
• Original Assignee: Ofinno Technologies, LLC
• Inventors: Dinan, Esmael Hejazi
• Primary Examiner(s): Ngo, Ricky
• Assistant Examiner(s): NG, CHRISTINE Y
• Application Number:
  US13/662,487
• Publication Number:
  US 20130107827A1
• Time in Patent Office: 667 Days
• Field of Search: 370/328, 370/329, 370/338, 370/350, 370/401
• US Class Current: 370/329
• CPC Class Codes: H04H 20/42 Arrangements for resource management
• CPC Class Codes: H04J 11/00 Orthogonal multiplex systems, e.g. using WALSH codesH04J13/00 takes precedence
• CPC Class Codes: H04L 69/22 Parsing or analysis of headers
• CPC Class Codes: H04W 16/32 Hierarchical cell structures
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A network comprises a plurality of base stations. Transmission time is divided into a plurality of frames and each frame is assigned a system frame number. A base station transmits the system frame number and a synchronization signal during each frame. The transmission of the synchronization signals are substantially time aligned among the plurality of base stations. Base stations transmit the same system frame number in frames that are transmitted substantially at the same time.

Claims

1. A method comprising:

a) transmitting, by each base station in a plurality of base stations, during each frame in a plurality of frames, a system frame number (SFN) assigned to said frame; and

b) transmitting, by each base station in said plurality of base stations, during each frame in said plurality of frames, a synchronization signal indicating a cell ID, the transmission of said synchronization signals being substantially time aligned among said plurality of base stations; and

c) transmitting, by each base station in said plurality of base stations, a message to a plurality of wireless devices in connected mode, for each of said plurality of base stations, said message comprising;

i) a subframe allocation repetition period in terms of p frames, p being an integer greater than or equal to one;

ii) a subframe allocation offset i, i being an integer greater than or equal to zero; and

iii) a subframe allocation bitmap indicating a plurality of subframes in k frames, k being an integer where 1≦

k≦

p, said bitmap applying to subframes in k frames starting from frames whose SFN meets (SFN mod p=i) criterion, said plurality of subframes comprising a first plurality of special subframes, during a majority of symbols of a special subframe of a base station;

(1) no signal is transmitted by said base station;

or

(2) signals are transmitted at a special subframe power level that is substantially lower than a transmit power during a non-special subframe; and

wherein all the base stations in said plurality of base stations transmit the same system frame number in frames that are transmitted substantially at the same time.

2. The method of claim 1, further comprising, transmitting in said special subframe, a common reference signal only in a control region.

3. The method of claim 1, wherein p is equal to 2^j and j is one of the following numbers:

0, 1, 2, 3, 4, and 5.

4. The method of claim 1, wherein said message is broadcast employing a physical downlink shared channel.

5. The method of claim 1, wherein a first base station decreases the number of special subframes in said first plurality of special subframes in response to an increase in the traffic load of said first base station by an amount greater than a load value.

6. The method of claim 1, wherein a first base station increases the number of special subframes in said first plurality of special subframes in response to a decrease in the traffic load of said first base station by an amount greater than a load value.

7. A method for operating each base station in a plurality of base stations, said method comprising:

a) transmitting, in each frame in a plurality of frames, the n most significant bits of a system frame number assigned to said frame, transmission of said n most significant bits employing a plurality of OFDM subcarriers in the middle of the frequency band of a carrier, said system frame number (SFN) being represented by m bits;

b) transmitting the (m−

n) least significant bits of said system frame number by encoding control blocks in a physical broadcast channel over 2<sup>(m−

n)</sup>frames, sequential position of said encoded control blocks determining the (m−

n) least significant bits; and

c) transmitting during each frame in said plurality of frames, a synchronization signal indicating a cell ID, transmission of said synchronization signal of each base station in said plurality of base stations substantially time aligned with transmission of other synchronization signals of other base stations in said plurality of base stations; and

wherein all the base stations in said plurality of base stations transmit the same system frame number in frames that are transmitted substantially at the same time.

8. The method of claim 7, wherein said synchronization signal comprises a primary synchronization signal and a secondary synchronization signal.

9. The method of claim 8, wherein said primary synchronization signal is generated using a frequency-domain Zadoff-Chu sequence.

10. The method of claim 8, wherein said primary synchronization signal is mapped to the last OFDM symbol in slots 0 and 10 for an FDD frame structure.

11. The method of claim 8, wherein said primary synchronization signal is mapped to the third OFDM symbol in subframes 1 and 6 for a TDD frame structure.

12. The method of claim 8, wherein said secondary synchronization signal is generated using an interleaved concatenation of two 31 bit length sequences.

13. The method of claim 12, wherein said concatenated sequence is scrambled with a scrambling sequence provided by the primary synchronization signal.

14. The method of claim 8, wherein said secondary synchronization signal differs between subframe 0 and subframe 5.