What we will talk about and who is doing the talking

Transcription

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2 What we will talk about and who is doing the talking

3 Vice President of Technology CoachComm LLC. Auburn, AL 30 years of RF and wireless technology experience Rental Mgr, Freelance RF, Product Mgr wireless/wired intercom, Engineering Mgr, Speaker, Author Systems Wireless, DTC, Talamas, Telex/RTS, CoachComm CoachComm designs and manufacturers Tempest wireless intercom CoachComm has two main markets Sideline football coach communications For Universities, Colleges, High Schools, and other programs Wireless communications for Broadcast, Live, and Industrial Applications Distributed by Clear-Com worldwide

4 The current state of the UHF spectrum Changes in regulations Less spectrum to go around Additional users vying for space Potential alternatives to UHF spectrum unlicensed spectrum Technology challenges and considerations related to unlicensed wireless use Digital RF techniques to overcome these challenges Practical tips and recommendations

5 UHF Spectrum Use Things are not getting easier in our traditional spectrum

6 Initial auction eliminated 108MHz of UHF spectrum MHZ gone - AT&T, Verizon, etc Incentive Auction looming Nobody really knows what s going to happen Likely at least another 100MHz or more gone White Space devices The great unknown! UHF and VHF, mobile and fixed Much less spectrum many more users Production demands for wireless aren t going down Other non-production devices added in

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9 All wireless audio devices are not created equal On-air devices Wireless microphones primarily Extremely low latency Audio frequency response 40Hz 12kHz or better Audio dynamic range 90dB or better Extremely high fade margin Extremely low tolerance for hits FM analog UHF only real option at this time

10 Talent devices Wireless IFB, In-ear monitors primarily Very low latency Audio frequency response 80 8kHz or better Audio dynamic range 90dB or better High fade margin Low tolerance for hits Very few options other than FM analog UHF at this time

11 Communication devices Wireless intercom primarily Some latency acceptable Audio frequency response 300 4kHz or better Audio dynamic range 80dB or better Lower fade margin Higher tolerance for hits cannot compromise communications Non-UHF options are available Some are even better than current UHF implementations Good candidate to migrate out of UHF spectrum

12 UHF wireless intercom is spectrally inefficient 8 wireless beltpacks use between 12 and 16 frequencies Requires free spectrum in different locations Migrating UHF wireless frees up a LOT of spectrum Moving 8 UHF wireless intercom beltpacks frees up 12 to 16 UHF frequencies for wireless mics/ifbs Huge impact on ability to provide wireless mics/ifbs Moving wireless intercom out of UHF is smart

13 If not the traditional UHF spectrum, where do we operate

14 Some available options MHz (900MHz) MHz (1.9GHz) MHz (2.4GHz) MHz (5.8GHz) Which is best All have advantages and disadvantages

15 World-wide operation 900MHz North America, Australia, some of South America 1.9GHz Most areas of the world spectrum varies from place to place 1880MHz 1900MHz in Europe 1900MHz-1920MHz in China 1910MHz-1930MHz in Latin America 1920MHz 1930 MHz in US/Canada 2.4GHz World-wide approval spectrum is generally the same Some limitations 5.8GHz Approval varies widely and is changing quickly

16 Amount of spectrum available 900MHz 26MHz 1.9GHz 10 to 20MHz depending on location US only 10MHz 2.4GHz 80 to 95MHz with very few exceptions 5.8GHz 150MHz or more but varies

17 Propagation characteristics Generally, higher frequency = poorer propagation 900MHz acts more like traditional UHF 5.8GHz suffers from body shielding and severe multipath 1.9GHz and 2.4GHz strike a balance Regulatory constraints transmitter power, modulation techniques, interoperability requirements 900MHz, 2.4GHz, 5.8GHz sharing mandated 1.9GHz somewhat similar, audio only

18 Competition for spectrum use Virtually all of these bands are being heavily utilized Licensing requirements All of these bands do not require a license for use Conclusion 2.4GHz offers the best balance of all factors for world-wide use 900MHz offers a good alternative for North America Technology is readily available for both Several manufacturers have adopted one or both

19 The challenges and solutions to working in an unlicensed spectrum

20 Lots of users vying for spectrum Wi-Fi b/g Bluetooth Wireless cameras Wireless DMX Microwave ovens Many Others Limited propagation characteristics More problematic with 2.4GHz than 900MHz Multipath fading Object penetration (900MHz is much better in this regard)

21 Regulations require devices to share Spread spectrum technology Major spread spectrum technologies Frequency Hopping (FHSS) Bluetooth Some wireless cameras Some wireless intercoms Direct Sequence (DSSS) & Orthogonal Frequency-Division Multiplexing (OFDM) Wi-Fi, b/g/n etc. Devices that ride along on Wi-Fi

22 What is FHSS Seeks to use as much spectrum as possible over time Uses a very narrow portion of the spectrum at any instance Narrow band transmission Changes frequencies hops periodically Pseudorandom hopping pattern Sequence must be known by base and remote Remote must be synchronized paired with base prior to use FHSS implementations vary greatly Some are more successful than others

23 Over time 80MHz of spectrum is used MHz Only 1.3MHz is used at one time Narrowband operation Wi-Fi is 20 or 22 or 40 MHz Changes frequencies or hops 200 times/sec 5ms dwell time

24 Gaussian Frequency Shift Keying (GFSK) Relatively simple modulation scheme Uses optimal modulation index Enhance receiver sensitivity in presence of noise Resists narrowband fading (Rayleigh fading) Narrowband transmission Concentrates RF energy in one specific area of spectrum Maintain robust wireless link in the face of interference and noise

25 Changing frequencies hopping Less susceptible to single point external interference sources Intermodulation products Multipath fading (Rayleigh fading) FHSS is inherently 1 to 1 technology Time Domain Multiple Access (TDMA) Enables multiple users All users operate on the same frequency Users share the frequency one at a time

26 Very different from FHSS Does not seek to use as much spectrum as possible over time Spreads RF power over a wider, fixed area Wideband transmission Spreading versus hopping

27 DSSS spreads the data using a pseudorandom noise signal Much higher frequency than data signal OFDM spreads the data using multiple orthogonal carriers Effectively produces a signal spectrally similar to DSSS but with many advantages Total RF power is similar to FHSS RF power at any given frequency is much less Resembles white noise to a well designed FHSS device De-spreading requires TX-RX synchronization Usually a timing search process

28 The FHSS system above may not work very well on its own Technology enhancements are necessary for robust, reliable operation Redundant Data Transmission (2xTX) 2.4GHz only All data is sent twice Once from each antenna On consecutive hops (different frequencies, different moments in time) Halves spectral efficiency

29 Redundant Data Transmission (2xTX) 2.4GHz only Dramatically reduces Effective Packet Error Rate (EERP) One RF packet loss is common Pseudorandom frequency hopping pattern separates consecutive transmissions This frequency relationship prevents multiple consecutive packet loss Two consecutive RF packets must be lost before an audio packet is lost Extremely important for 2.4GHz success

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32 Dual antenna diversity 2.4GHz only Adds spatial and polarization diversity to frequency and time diversity Makes for a very robust RF link Lost Packet Concealment (LPC) Packet loss is inevitable Allows some audio packets to be lost or damaged without noticeable impact on user audio Algebraic Code Excited Linear Prediction (A-CELP) At least four consecutive RF packet loss before an noticeable impact on audio is heard

33 The practical application of technology for success in the 2.4GHz and 900MHz bands

34 Can a well designed FHSS wireless intercom peacefully coexist with an extensive b/g/n Wi-Fi network? Yes Wi-Fi overview 14 channels world-wide 13 in most locations 11 in the US Each channel is 20 or 22 or 40 MHz wide (our FHSS 1.3MHz) Only 3 non-overlapping channels 1, 6, 11 (14 in Japan)

35 Wi-Fi uses 3 non-overlapping channels: 1, 6 and 11

36 Wi-Fi signal characteristics vary greatly depending on network traffic Worst case scenario is maximum network data throughput Signal appears to be higher power and more dispersed Normal web surfing does not typically produce this condition Even with lots of users Large file transfers create this condition Becoming more common as video streaming increases

37 Our FHSS/TDMA RF design with enhancements works and plays well with Wi-Fi RF power is concentrated into a small area of spectrum Wi-Fi RF power is spread over a much larger area of spectrum Wi-Fi appears as background noise to our FHSS design Greater perceived RF power at any given frequency allows our FHSS design to penetrate through the Wi-Fi signal Wi-Fi is not significantly affected by our FHSS design Each hop is a small portion of the Wi-Fi signal Spreading of the data means that all of the data gets through

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39 Best practices for coexistence Get as much physical distance as possible 50 feet minimum Consequences of coexistence Our FHSS system degradation Shortened range Digitized sounding audio Logging in and out b/g/n Wi-Fi Reduction of network throughput of 10% (90% capacity) Only noticeable at maximum network loading

40 Constrain our FHSS to a limited portion of the band Allows system to avoid one or more Wi-Fi chans Limits hoping pattern Usually best to use the whole band 7 bands available in our design MHz Band Chan Start End Wide Avoid b/g None , ,8,9,10, , ,2,3,4,5,6,7

41 2.4GHz Tempest One base supports up to 5 normal mode users One base supports an unlimited number of shared users Limited to five talkers per base at any given time Up to 11 collocated bases Up to 55 normal mode wireless users Unlimited number of shared mode wireless users

42 900MHz Tempest One base supports up to 5 normal mode users One base supports an unlimited number of shared users Limited to five talkers per base at any given time Up to 5 collocated bases Up to 25 normal mode wireless users Unlimited number of shared mode wireless users Mixed 900MHz/2.4GHz system Up to 80 total wireless full duplex users

43 The presentation in a nutshell

44 UHF spectrum is becoming much more crowded and will continue to do so Production requirements continually call for more wireless devices Migrating wireless microphone and/or wireless IFB equipment out of the traditional UHF band is not practical at this time Wireless communication equipment can be effectively migrated outside the UHF band

45 The 2.4GHz & 900MHz bands are excellent candidates for wireless communications Spread spectrum technology allows multiple users to better share a given portion of the spectrum Choosing the right implementation of spread spectrum technology is important FHSS technology wireless intercom systems help to enable collocation with b/g/n Wi-Fi and other devices Other technologies and techniques must be utilized in conjunction with the base FHSS/TDMA RF scheme

46 Any Questions?