Wireless simulator

• US 7,286,802 B2
• Filed: 02/14/2003
• Issued: 10/23/2007
• Est. Priority Date: 02/15/2002
• Status: Active Grant

• Current Assignee: Viavi Solutions, Inc. (Lumentum Holdings Inc.)
• Original Assignee: Dyaptive Systems, Inc. (Lumentum Holdings Inc.)
• Inventors: Sankey, Todd, Beyme, Steffen, Kilgour, Chris
• Primary Examiner(s): Milord; Marceau
• Application Number:
  US10/366,619
• Publication Number:
  US 20030236089A1
• Time in Patent Office: 1,712 Days
• Field of Search: 455/423, 455/424, 455/436, 455/67.11, 455/67.14, 455/67.16, 370/401, 370/336
• US Class Current: 455/67.14
• CPC Class Codes: H04B 17/0087 using auxiliary channels or channel simulators
• CPC Class Codes: H04B 17/309 Measuring or estimating channel quality parameters
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 52/04 TPC
• CPC Class Codes: H04W 52/60 using different transmission rates for TPC commands

Abstract

There is disclosed a simulator for mobile terminals within the context of a wireless network, for the purpose of testing the basestations. Channel impairments are effected during baseband processing.

Claims

1. A system to test a portion of a wireless communication network that provides a plurality of forward signals, comprising:

means for accepting said plurality of forward signals in a forward link, and for returning a plurality of reverse signals in a reverse link to the tested network portion that are suitable for direct input thereto without requiring modifications;

wherein said plurality of reverse signals has the properties of an equivalent signal that would be produced by a plurality of mobile terminals communicating with said tested network portion through a plurality of independent forward link channels and reverse link channels.

2. The system of claim 1, wherein said accepting and returning means for simulating a plurality of MTs implemented on a generic, communications protocol-agnostic SDR hardware platform;

said plurality of SMTs behave as would real MTs in the presence of said forward link that includes the macroscopic effects of forward channel impairments; and

said reverse link includes the macroscopic effects of reverse channel impairments achieved by performing certain calculations on the baseband signal.

3. The system of claim 2, wherein said reverse link is effected by simulating the effects of impairments to each said reverse channel as introduced into some part of the transmitting chain of each said SMT.

4. The system of claim 2, wherein said channel impairment includes the simulation of mobility of at least one SMT corresponding to the physical movement of a MT.

5. The system of claim 4, wherein said channel impairments reflect features of a specific physical environment.

6. The system of claim 5, wherein, for each SMT-sector combination, said channel impairment includes the simulation of one of, {(a) mean path loss (MPL), (b) large-scale fading loss, (c) small-scale fading loss, (d) lumped-parameter phase rotation and (e) time delay}.

7. The system of claim 6, wherein MPL is defined by configuration parameters and real-time parameters.

8. The system of claim 7, wherein MPL configuration parameters include one of {SMT antenna gain, SMT instantaneous band class, SMT instantaneous carrier frequency, and the applicable MT Class}.

9. The system of claim 8, wherein MPL real-time parameters include one of {BTS sector antenna gain, BTS-SMT line of sight distance, BTS sector raw pilot strength(s) and BTS sector raw output power}.

10. The system of claim 6, wherein small-scale loss is due to propagation impairments that are small compared to the carrier wavelength to introduce effects like multipath and Doppler effects.

11. The system of claim 4, wherein mobility simulation is effected by providing the functions of a second basestation, and said two bastations are coordinated, in conjunction with one said SMT whose simulated signals are characterized in the RF domain as an MT being in the effective transmission range of two basestations, wherein said (forward and reverse) channel simulations and pilot management are performed to effect a soft handoff.

12. The system of claim 2, further comprising a scenario/channel simulation engine for creating a real time simulation of a plurality of MTs interacting with the tested network portion.

13. The system of claim 12, comparing means for defining a script of channel impairments for said scenario/channel simulation engine.

14. The system of claim 13, further comprising means for assigning said defined script to a SMT/MTS.

15. The system of claim 14, further comprising means for activating said assigned script.

16. The system of claim 15, wherein groups of SMTs are scripted to perform similarly.

17. The system of claim 2, wherein said simulation includes the sharing of functions and processing steps of SMTs during baseband processing.

18. The system of claim 17, wherein said simulation is effected by simulating all RF paths between said basestation and a plurality of SMTs, by combining and scaling all individual RF carriers.

19. The system of claim 18, wherein said first basestation functions are sectorized, and where in the forward direction, the received signals R at an SMT is the product of gain G and sector signals S, where G is adjusted to reflect impairments such as time varying propagation paths in the RF domain.

20. The system of claim 19, wherein in said forward link, said channel simulation includes mathematically approximating channel impairments.

21. The system of claim 20, wherein said approximating is done by sampling at granularity of chip-rate.

22. The system of claim 20, wherein said approximating is done by sampling at granularity of power control rate.

23. The system of claim 20, wherein said approximating is done by sampling at granularity of frames or groups of symbols.

24. The system of claim 20 wherein said approximating is done by sampling at power control rate for one channel and chip rate simulation for another channel.

25. The system of claim 2, where in said forward link, said channel simulation includes scaling of the energy contribution of each basestation sector and the interference levels.

26. The system of claim 2, wherein in said forward or reverse link, said channel simulation includes calculating elements of one of said communication protocols.

27. The system of claim 26, wherein one said calculated element is the desired pilot strength Ec/Io at each SMT being calculated once and sent to all SMTs (instead of being measured by each SMT).

28. The system of claim 27, where the calculation is by appropriate sector scaling G.

29. The system of claim 28, wherein in said reverse link, said channel simulation combines power control and channel simulation (G′

=G×

R/R0) where R=KR0.

30. The system of claim 2, where all demodulation and decoding of shared channels for all SMTs is done by a single, shared hardware/firmware resource.

31. The system of claim 30, where in the distribution of symbols in all SMTs is only indirectly simulated as BER, and where relative sector power (pilot strength) does not actually change when simulating soft(er) handoff.

32. The system claim 31, wherein the reverse links of a plurality of a plurality of SMTs operating on the same carrier are combined at baseband and the subsequent combined signal is filtered and digitally upconverted to an IF or the desired RF.

33. The system of claim 32, wherein the combination and accumulation is distributed among the individual SMTs connected by a multiplex bus or tree.

34. The system of claim 2, wherein said SMT simulation means includes a MT simulator (MTS) being a software/hardware cradle for hosting a SMT.

35. The system of claim 34, further comprising controller means, in a communication link with said MTS, for instantiating a SMT in said MTS.

36. The system of claim 35, where said MTS is directly connected to BTS sector ports.

37. The system of claim 36, wherein for a BTS having n sectors, a MTS has at least n+1 connections.

38. The system of claim 34, wherein said SMT has state information for it to operate within a MTS.

39. The system of claim 38, wherein said communications link between said MTS and said controller means has a throughput capability greater than that in a typical MT/BTS communications.

40. The system of claim 39, wherein said controller means can send override commands to the SMT/MTS, for creating conditions that are abnormal for a properly operating MT.

41. The system of claim 1 or 2, wherein said forward link is effected by simulating the effects of impairments to each said channel as introduced into some part of the receiving chain of each said SMT.

42. The system of claim 1, wherein the tested network portion includes means for producing network access point functions.

43. The system of claim 1, wherein the tested network portion includes means for producing functions of a first basestation.

44. The system of claim 1, wherein two of said channels operate on different communications protocols.

45. The system of claim 44, where one of the protocols is one of {FDMA, CDMA, W-CDMA, UMTS and derivatives thereof}.

46. The system of claim 1, wherein signals transmitted on two of said channels are the subject of different encoding and decoding methods.

47. The system of claim 1, wherein signals transmitted on two of said channels are carried on different frequencies.

48. The system of claim 1, wherein two of said channels have different bandwidths.

49. The system of claim 1, wherein said channel simulations are effected in part by the application of an impairment of said forward link or said reverse link of one said channel.

50. The system of claim 1 wherein the tested network portion includes means for providing the functions of a second basestation and further comprises means for simulating two-way communications between said second basestation function means, and one of said plurality of SMTs.

51. The system of claim 50, further comprising means for coordinating and controlling said first and second basestation function means.

52. The system of claim 50, wherein said MTS is in direct communication with said two basestations.

53. The system of claim 52, wherein said moving is accomplished by instantiating the SMT in the second MTS by copying state information from first MTS to second MTS.

54. The system of claim 50, comprising a plurality of MTSs and a plurality of basestations, wherein each said MTS is in direct communication with at least two of said basestations, and where mobility simulation is effected by moving one said SMT from one said MTS to a second said MTS.

55. The system of claim 1, wherein said forward link channel includes the following sequential steps:

(a) processing RF to digital baseband

(b) processing digital baseband to chip

(c) processing chips to symbols

(I) sector scaling and combining

(II) chip-rate channel simulation

(III) power-control rate channel simulation

(d) processing symbols to frames.

56. The system of claim 1, wherein said reverse link channel includes the following sequential steps:

(a) processing frames to symbols

(b) processing symbols to spread signals

(c) channel simulation, sector scaling and combining

(I) channel simulation

(II) combined power control and channel simulation

(III) sector scaling and combining

(d) processing chips to RF.

57. The system of claim 1, wherein a channel profile is created to be a time-varying vector of channel simulation parameters.

58. The system of claim 57, wherein channel simulation parameters include those for simple and complex fading.

59. The system of claim 57, wherein channel simulation parameters are created on a per-SMT and per BTS sector basis.

60. The system of claim 59, wherein for each SMT-sector combination, channel simulation includes one of {(a) mean path loss (MPL), (b) large-scale fading loss, (c) small-scale fading loss, and (d) lumped-parameter phase rotation and (e) time delay}.

61. The system of claim 60, wherein MPL is defined by configuration parameters and real-time parameters.

62. The system of claim 61, wherein MPL configuration parameters include:

SMT antenna gain, SMT instantaneous band class, SMT instantaneous carrier frequency, and the applicable MT Class).

63. The system of claim 61, wherein MPL real-time parameters include:

BTS sector antenna gain, BTS-SMT line of sight distance, BTS sector raw pilot strength(s) and BTS sector raw output power.

64. The system of claim 63, wherein small-scale fading is due to propagation impairments that are small compared to the carrier wavelength and introduce effects like multipath and Doppler.

65. The system of claim 57, wherein static channel simulation parameters include one of the following:

{calibrated transceiver conversion gain and connection loss between each BTS sector and the SMT}.

66. The system of claim 1, further comprising means for interfacing with test equipment.

67. The system of claim 1 comprising means for interfacing with a PC.

68. The system of claim 1, further comprising an antenna and wherein said SMT is connected to said antenna.

69. The method of testing a portion of a wireless communication network that provides a plurality of forward signals, comprising the steps of:

accepting said plurality of forward signals in a forward link, and returning a plurality of reverse signals in a reverse link to the tested network portion that are suitable for direct input thereto without requiring modification;

wherein said plurality of reverse signals has the properties of an equivalent signal that would be produced by a plurality of mobile terminals communicating with said tested network portion through a plurality of independent forward link channels and reverse link channels.