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Improving
Wireless Access Technologies
Adam WoliszProfessor of EE&CS, Technische Universität Berlin,
TKN Adjunct Professor, EE&CS Dept, UC Berkeley,
BWRC http://www.tkn.tu-berlin.de/~wolisz/wolisz.html
Sept.26,2007
TKN Telecommunication Networks Group 2
Overview
Short introduction of the TU Berlin research environment
Towards Dynamic OFDM (OFDMA)
Dynamic spectrum usage with Cognitive Radios
TKN Telecommunication Networks Group 3
The contribution of my collaborators/students notably
TUBerlin: Dr. Gross, Mathias Bohge, Oscar Punal, Daniel Willkomm, Murad
Abusbeih
UCBerkeley: Prof. Brodersen, Dr. Cabric, Mubaraq Mishra
ST Microelectronics: Wendong HU, Dr. George Vlantis
Is gratefully acknowledged.
Acknowledgements:
TKN Telecommunication Networks Group 4
Main-CampusBerlin University of Technology
TKN Telecommunication Networks Group 5
Established in April 2001 as a pilot fusion of EE and CS.
43 associate or full professors (German C4 or C3) + a numerous “Professors in Residence”
3 curricula (Number of beginners/Year, trend)EE (260+), CE (150+), CS (300+-)
Communication Technology is one of the major focus areas – for the whole TUB.
TU Berlin: The Faculty of EE&CS
TKN Telecommunication Networks Group 6
Communications Research relevant environment
COOPERATION: 21 joint faculty appointments;incl.17 fully funded by partners
The Institutes in 2004 total budget of € 165m,
(€110m in external grants) 1800 employees, incl.
380 employees with a PhD
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TUBerlin
TKN Telecommunication Networks Group 7
Telecommunication Networks Group (TKN) People: Full professor (Chair) A. Wolisz + (2-4) Post-Docs / Assistant Professors + (20-25) Research Assistants/PhD students + 3 Technical Staff + 2 administrative assistants
Supported by grants from: EU, BMBF, DFG, DAAD, Siemens AG, Ericsson, DoCoMo, ....
External Funding – approx. 1.5 Mio €/Year
Som-2006e numbers for the time 20009 post-doc research associates/Phd Graduates/adjunct lectureres have been appointed professors. Degrees granted: Doctorate: 20 , Diplomae: Over 90
Papers: ca. 50 in journals, magazines or book chapters ca. 150 in refereed conferences/workshops
see www.tkn.tu-berlin.de/publications
TKN Telecommunication Networks Group 8
Research Topics (selection)General Direction:
Architectures and Protocols for Networks
Optical backbone/ Optical Metro Networks...
Wireless access...(QoS + Capacity).
Mobility incl. Group mobility and High speed mobility
Sensor networks
Cognitive Radio
TKN Telecommunication Networks Group 9
The Fundamental Problem
Wireless dominates last hop (s?) Because cable is always a constraint...
Two fundamental features of wireless communication:
Interference; i.e. influence of any transmission on other ones calling for proper Separation (space, Frequency, time, code)
Dynamic change of the received signal strength in spite of constant transmission power even without interference.
These features result in challenges:
Limited Capacity, given frequency spectrum and space.
Difficulties in proper QoS support even on a single link
TKN Telecommunication Networks Group 10
Introduction: OFDM
Orthogonal Frequency Division Multiplexing (OFDM) splits the bandwidth into narrowband sub-carriers
Parallel symbol transmission (reduces intersymbol interference)
Orthogonal sub-carriers (no intercarrier interference) Fading produces a strong variation in the sub-carrier gains: always some sub-carriers in a “bad state”
Orthogonal Frequency Division Multiplexing
This changes in the time domain as well…
TKN Telecommunication Networks Group 11
Basic Scenario
Terminals
Access Point
Backbone
Downlink
Data Queues at Access Point
OFDM as transmission scheme!
TKN Telecommunication Networks Group 12
Link Adaptation
IEEE 802.11 a/g : Time division Multiple Access and adaptive modulation/coding - the same over all sub-carriers.
Average channel gain adaptation: the few sub-carriers with the lowest gain dominate the BER & PER [Awoniyi06] • Same Modulation and
Coding Scheme on all Sub-carriers, which are assigned to one station
TKN Telecommunication Networks Group 13
Adaptive Modulation Scheme
For each individual sub-carrier the selected modulation schema assures the highest bit-rate for upper-bounded BER.
TKN Telecommunication Networks Group 14
Dynamic OFDM: Adaptive Modulation
Adapts the modulation type to the current gain of each sub-carrier subject to a bit error probability target, performing adaptation on a per-packet base.
Theoretically this procedure has been shown to outperform Link Adaptation [Czylwik98]
Assignments:
NO MOD. SNRx ≤ Xi
BPSK Xi < SNRx < Xj
QPSK Xj ≤ SNRx < Xk
…
BPSKSub-Carrier 1
16-QAMSub-Carrier 2
BPSKSub-Carrier 3
BPSKSub-Carrier 4
64-QAMSub-Carrier 43
QPSKSub-Carrier 44
64-QAMSub-Carrier 45
BPSKSub-Carrier 46
16-QAMSub-Carrier 47
QPSKSub-Carrier 48
ST
A 1
TKN Telecommunication Networks Group 15
Dynamic OFDMA
Performance Improvement [Wong99]
The whole set of sub-carriers is split into sub-groups, which are then assigned to different stations in a FDM fashion.
STA
2ST
A 2
STA
1ST
A 3
MULTI-USER DIVERSITY
BPSKSub-Carrier 1
16-QAMSub-Carrier 2
BPSKSub-Carrier 3
BPSKSub-Carrier 4
64-QAMSub-Carrier 43
QPSKSub-Carrier 44
64-QAMSub-Carrier 45
BPSKSub-Carrier 46
16-QAMSub-Carrier 47
QPSKSub-Carrier 48
TKN Telecommunication Networks Group 16
Now: Optimization approach Open question: How to generate the subsets of
sub-carriers serving individual flows?
Two-step approach (Yin et al. 2000) per time SLOT.
First: sub-carrier allocation
- Determine the number of sub-carriers for each subset
(meeting the demand)
- IDEA: Utilize packet queue…
Second: sub-carrier assignment
- Choose sub-carriers according to the allocated number for each subset
- IDEA: Utilize channel-related information for the assignment
(goal: increase the capacity, assure fairness)
TKN Telecommunication Networks Group 17
Allocation: satisfying the demand...
Let us assume ONE Queue per terminal (i.e. flow)The queue will built up if bad transmission ...
Packets should be dropped if waiting excessively. Observation: Not all frames in an MPEG video are equally important (I, B, P frames)
Drop packets based on importance: I frames on deadline, P frames 25% earlier, B frames 50% earlier.
Allocate the bit-rates (simplified: NUMBER of sub-carriers) based on weighted lengths of queues
The size of important packets is given a larger weight ...
Queue length is the sum of these weights
TKN Telecommunication Networks Group 18
Assignment: Integer Programming Formulation
More flexibility by formulating assignment as Integer Program
{1,...,J} : Set of wireless terminals,
{1,...,S} : Set of sub-carriers
gj,s: CNR of terminal j on sub-carrier s
ps : power assignment for sub-carrier s
F(): Mapping of subcarrier SNR to applied modulation type
cj,s:(= 0,1): Assignment of sub-carrier s to terminal j
zj: Subcarrier allocation for terminal j
Basic formulation:
sjsj
jsj
sj zcj
cscCtosubject
,
,
, :
1::
sj
sjssjcC
gpFcsj ,
,,)( ,
maxMaximize capacity
Each subcarrier
only assigned
once
Number of sub-carriers perterminal fixed
out ofAllocation!
TKN Telecommunication Networks Group 19
Optimal solution (constant power assignments)
Assignment problem maps to a graph theoretical problem
Maximum weight bipartite matching problem
An optimal algorithm for this problem exists – the Hungarian algorithm with complexity of O(S3)
Measured run times of the algorithm: ~2ms are too long compared to the Allocation/Assignment
TIME SLOTS < coherence time of wireless channels in our test data
Good heuristics exist for this problem, solving the problem with average parameter setting within 500µsPerformance loss: 10%
TKN Telecommunication Networks Group 20
AssignedSub-Carrier Set of
User 3
AssignedSub-Carrier Set of
User 2
AssignedSub-Carrier Set of
User 1
A heurisitc for the Assignment...
1 2 3 4 5 6 7 8 9 10 11 12
G
B
B
G
G
G
G
G
G
G
G
B
B
G
G
G
G
G
G
G
G
G
G
G
G
G
B
G
B
B
B
G
G
B
G
B
Sub-Carriers
User 1
User 2
User 3
Single Sub-CarrierStates towards:
Sub-CarrierWeight:
1 3 3 2 2 3 3 3 2 1 2 1
Dynamic FDM assignment of sets of sub-carriers to individual terminals
TKN Telecommunication Networks Group 21
Numerous results addressing:
Joint optimization of power (loading) and assignment. Including the overhead for signaling (how should the
receiver now which sub-carriers have been assigned?) Allocation including priorities See our URL…==============================================================
=====
But: does this require completely new systems? We suggest the Adaptive Modulation in the up-link
and Dynamic OFDMA in the down-link… A proposal for including this to IEEE 802.11… as
backward compatible solution.
- Technical Report: TKN-07-002
- Submissions to IEEE 802.11, VHT SG
TKN Telecommunication Networks Group 22
Required changes to use Dynamic OFDM
In order to choose an (optimal) modulation/coding per sub-carrier, we need to
- - estimate the channel gain per sub-carrierfor each transmission Obligatory RTS/CTS
- inform the receiver about modulation/coding used per sub-carrier extended header in data packets
- adjust the NAV settings after the transmission For the multi-user case (parallel transmission of packets), we
have to add Multiple CTS per RTS and ACKS per data packet
- multtiple CTS per RTS, and ACKS per data packet; signal the assignment of sub-carrier sets,
Higher Performance but also higher processing power.
TKN Telecommunication Networks Group 23
Schemata of the changes
Single user
Multi-user
TKN Telecommunication Networks Group 24
Some performance data (simulation!)
• Simulation Settings:
- Saturation mode,
- 4 and 8 stations,
- downlink traffic
• Scenarios: – Multi-user mode
– Single-user mode with Round Robin Scheduling
– 802.11 a/g with RTS/CTS and Round Robin Scheduling
• Metrics:
– Goodput, PER and PHY Efficiency
TKN Telecommunication Networks Group 25
This approach has potential…
Goodput - 8 STAs - Large Packets (1564 Byte) - 802.11 a/g with RTS/CTS
Goodput - 4 STAs - Large Packets (1564 Byte) - 802.11 a/g with RTS/CTS
TKN Telecommunication Networks Group 26
Ongoing work …
We have proposed recently a proposal for the interface definition and API between MAC-PHY
3FPP LTE simulator (Ericsson) – used for sensitivity of the system efficiency on the Control Channel error due to interference from neighbor cells…
The real overhead, inaccuracies of sub-channel estimations, etc. require experimental investigation.
Several PHY developments (FPGA based) in preparation.
Execution of the algorithms on FPGA platforms is to be considered.
TKN Telecommunication Networks Group 27
The underlying philosophy: Using the best opportunity.
Why not use the same philosophy for grabbing more spectrum…
This is Cognitive Radio based spectrum utilization…
TKN Telecommunication Networks Group 28
Nutrition facts: The bad news...
The amount of non-licensed spectrum (in interesting frequencies) is limited
3 4 5 6 GHz Allocation in the 3GHz-6GHz
TKN Telecommunication Networks Group 29
Nutrition facts: The good news...
Licensed users do not REALLY use ALL THEIR spectrum ALL the time in EACH place the license holds
The estimates are like 80%? 90%? 99%? unused...
A snapshot from Berkeley: real measurements…
TKN Telecommunication Networks Group 30
Re-Usage of sectrum: What are the options? The licensed users – called PRIMARY USERS – could be
screened, andBe permitted to “sell” or “lease” their licenses….
Loose licenses (for some area) if spectrum not used properly
Have licenses limited to some times of the day“recycled” assignments could be opened as ISM bands
The primary user (or a “broker” on their behalf) could be obliged to “announce” unused frequencies (again in space and time domain); usage as ISM bands is possible.
A new category of users - SECONDARY USERS - possess the ability to assess autonomously the temporarily unused spectrum and grab it for “specific” usage without primary users being aware of this “kidnapping”
TKN Telecommunication Networks Group 31
A Primary User X … legally owns some frequency band
… can tolerate a maximal interference time tx each time he resumes channel usage
A secondary user system has tx time units to detect a primary user and clear the corresponding Sub-Channels (time domain!)
tx is dependent on the primary user system and may vary from system to system
… is not (cognitive) secondary radio aware (i.e. does not provide specially signaling of activity – especially no preparation to re-gain his frequency band)
NOTE: IF primary user would use a carrier sensing protocol, neglecting the (unknown!) secondary user MUST be assured (operation below the carrier sense sensitivity!)
TKN Telecommunication Networks Group 32
Cognitive radio for “Secondary Users”
TKN Telecommunication Networks Group 33
Sensing while sending??? (a system view)
A fundamental challenge … three possible answers
Interrupted sending… (see e.g. IEEE 802.22 basic…)
Quick sensing needed.
Bad for QoS of the secondary's
Part of the “primary” band not re-used (see Corvus)
Coordination of frequency usage required
Band only partially available for sensing…
TKN Telecommunication Networks Group 34
Interleaved frequency usage (see CORVUS) Active primary user
Hz
Sub-channel
Primary user frequency band (F-Band)
Secondary user link (SUL)
Bandwidth B [Hz]
SUs compose SU-Links out of free sub-channels
Sub-channels of active Primary users (Pus) can't be used by SUs
PU F-Band covers multiple sub-channels
New sub-channels should be acquired
Divided into N sub-channels of bandwidth b=B/N [Hz]
(Re-)appearance of PU All affected Sub-Channels have to be cleared
TKN Telecommunication Networks Group 35
This resembles OFDMA… sure:
Efficiency: Potential for usage of the spatial diversity (anyway in downlink)Available actual bandwidth of each sub-carrier (depending on the channel conditions) fully utilized.
Constant Sub-carrier SpacingRobust to channel positioning (offset) and bandwidth changes
Interesting options for usage for the secondary devices in the “Interleaved transmission” modus.
TKN Telecommunication Networks Group 36
Sensing while sending??? (a system view) cont.
A fundamental challenge … three possible answers
Interrupted sending… (see e.g. IEEE 802.22 basic…)Quick sensing needed.
Bad for QoS of the secondaries
Part of the “primary” band not re-used (see Corvus) Coordination of fre-quency usage required.
Band only partially available for sensing…
Regular hopping (see e.g. IEEE 802.22 DFH mode)
Changing frequency bands regular event (collision in 802.3)
“Relaxed” sensing in free(?) band – assuming coordination
TKN Telecommunication Networks Group 37
IEEE 802.22 (DFH)
Worldwide first draft of a Cognitive Radio standardProvide wireless broadband Internet access using TV-bands
Ensure non interference with incumbents (grace period 2s) through spectrum sensing -
Philosophy following WiMax (IEEE 802.16)
Basic Mode: Assure respecting the grace period by sensing during TRANSMISSION INTERRUPTION
DFH: Perform data transmission and sensing in parallelTransmit data on channel X and perform sensing on channel Y
After 2 seconds channel Y is used for data transmission and the next channel is sensed. Might be X again...2 channels/cell
Thus an 802.22 cell hops through a set of working channels
TKN Telecommunication Networks Group 38
DFHC (DFH Communities) – some ideas
Each community has a community leader Leader is selected through leader election
Leader calculates a hopping pattern for each member of the community (i.e. cell)
Leader is responsible for accepting / rejecting new members
Neighborhood discoveryOne-hop broadcast of used frequencies and current interference situation by all 802.22 cells
Used to create and maintain communities
It is possible to support N Cells with (N+1) frequencies…
TKN Telecommunication Networks Group 39
DFHC hopping pattern
W. Hu, D. Willkomm, L. Chu, M. Abusubaih, J. Gross, G. Vlantis, M. Gerla, and A. Wolisz, "Dynamic Frequency Hopping Communities for Efficient IEEE 802.22 Operation", IEEE Communications Magazine, Special Issue: "Cognitive Radios for Dynamic Spectrum Access", May 2007
Cells need to shift their operation periods by one quiet time
Quiet time is the minimum time needed to sense a channel
Ch A
Ch B
Ch C
WRAN 1
WRAN 1
WRAN 1
WRAN 1
WRAN 1
WRAN 2WRAN 2
WRAN 2
WRAN 2
WRAN 2
Quiet Time Operation Periond
Ch D WRAN 1
WRAN 1
WRAN 2 WRAN 2 WRAN 1
WRAN 1WRAN 3
WRAN 3
WRAN 2
WRAN 2
WRAN 3
WRAN 3
WRAN 3
WRAN 3
WRAN 3
WRAN 3
WRAN2 WRAN1
WRAN3
TKN Telecommunication Networks Group 40
Protocol sketch for schedule maintenance
Hopping patterns can changeDue to incumbent appearance on a used channel
Due to a member leaving / joining a community
Community leader needs to calculate new hopping pattern and distribute it in the community
Consistency issue: How to assure that all members receive the new hopping information
If not all members switch to the new hopping pattern simultaneously there might be collisions between the old and the new hopping pattern
Solution: Hopping pattern lifetime and sequential switching
TKN Telecommunication Networks Group 41
Hopping pattern lifetime
Hopping patterns have a specific lifetime After expiration of the lifetime the hopping pattern
cannot be used anymore The leader thus has to periodically renew the
hopping pattern Upon renewal the pattern can be changed, new
members can be added, etc. This ensures consistency: even if some members do
not receive the new pattern, they cannot use the old one anymore
But what if a hopping pattern needs to be changed in the middle of a lifetime (i.e. due to appearance of an incumbent)?
Solution: Sequential Switching
TKN Telecommunication Networks Group 42
Sequential Switching The leader sequentially switches all members one
by one to the new hopping pattern New hopping pattern is collision free with the
pattern of all members not switched yet Implicit acknowledgement: sensing on the newly
assigned channel (implicit confirmation by acting) Even if somebody fails to follow - all members
already switched can use the new pattern without any collisions
TKN Telecommunication Networks Group 43
In any case: Detection of (possibly) Weak Signals
Cognitive radio observes (senses) primary system signals
Those might be strongly attenuated
While the transmission of the CR(Tx) towards Rx is not…
Primary User
Cognitive Radio users must guarantee non-interference requirement
distance
Distance and channel not known
Tx
Rx
CR(Tx)
CR(RX)
Decoding SNR Sensing SNR
TKN Telecommunication Networks Group 44
Solution: Network Spectrum Sensing [BWRC,Cabric]
Prob. of false alarm
Prob
. of d
etec
tion
1 radio
5 radios
If spacing >> λ/2 a few cooperative radios give big improvements
TKN Telecommunication Networks Group 45
We need a signaling channel:
Cooperation is needed… at least in “proximity”For assuring that “no other secondary is transmitting during the sensing”
For assuring network spectrum sensing.
Who should be subject to coordination?
How to organize the exchange of information for coordination??
TKN Telecommunication Networks Group 46
But: Control Channel needed (logically) for: Universal Control Channel (UCC)
Globally unique Used to get necessary information for creation of new
groups and to announce them Used by new users to choose and join a specific
Group Group Control Channel (GCC)
Each SUG has own control channel Used for exchange of sensing information – recognition
of primary users. Used for data channel establishment (out of
temporarily available resources) and its maintenance in spite of re-appearing primary users.
Numerous claims in favor of a specific Control Channel are recently being made…
TKN Telecommunication Networks Group 47
Options for the control channel implementation
An Universally/regionally pre-assigned frequency….
Globally unique Will be difficult….
ISM band…Globally available…What about possible (strong??) interference?
UWBNot interfering Tradeoff: distance vs. bit-rate might be very useful Cost? Deployment?
One of the “available channels”Convention for selection neededIEEE 802.22 considers this variant….
TKN Telecommunication Networks Group 48
BWRC Platform [BWRC: Cabric, Tkaczenko]
Sensing PHY real-time processor:
• 4 FPGAs ~ 10M gates ASIC at 250 MHz
• On-chip memory: Soft+Hard > 10 Mbits
• Dynamic Partial Reconfiguration
• Dedicated DSP blocks: 18b mult + MAC
• Architecture optimization for ASIC
- Parallelism/Pipelining/Interleaving
- Bitwidth optimization
- Area estimate: 10,000 slice = 1mm2
Sensing MAC embedded processor:• Central FPGA: Linux + Full IP
• Embedded processors: PPC+ARM
• On-chip Ethernet MAC
• Bus connection to 4 other FPGAs
Radio interfaces:• 16 high speed radio links (10 Gbps)
• 4 interfaces per FPGA
• Fiber optic cable compatible
TKN Telecommunication Networks Group 49
Reconfigurable Wireless Radio Modem [BWRC]
10 Gbps infiniband connectionsupports fiber optic cables
Sensing radioprocessor
Antenna
A/D 12b/64MHzD/A 14b/128MHz 2.4 GHz radio
(85 MHz) ISM band
Suitable for sensing and transmission in TDD mode
TKN Telecommunication Networks Group 50
Why 2.4GHz? Very crowded spectrum with unlicensed devices.
IEEE 802.11 b/g cards within laptops, are quite programmable and allow users to control their transmission parameters.
Easy to implement protocols on these cards
Hardware and software support for the 2.4GHz bands is already developed within BWRC
BWRC cards can be programmed to the complete 80MHz band
TKN Telecommunication Networks Group 51
First Experimental setup at 2.4GHz [BWRC/TKN]
BEE2 radios perform sensing
Laptops perform transmission
Laptops connect to the BEE2 via standard TCP/IP
TKN Telecommunication Networks Group 52
What about control channel ?? In first set-up:
“Internal communication” between sensing boards
Ethernet communication between the laptops…
One selected wireless channel, ot IEEE 802.11.a could also have been used.
This might be enough for SOME of the experiments…
==================================
Let us also keep in mind some (available) other option, the IEEE 802.15.4a CHIRP solution (Nanotron, Berlin)
Promises: A pretty robust transmission with range sufficient for WLAN type deployment…. + inherent (precise) LOCATION
Samples being in possession of TUBerlin/TKN for evaluation….
TKN Telecommunication Networks Group 53
Functions of „Classical Wireless Systems“
We will consider here: Cellular, infrastructure WLANs, ad-hoc networks…
What has been typical for all of them? (history)Usage of specific frequency bands optimized transmission
Exclusive usage of frequency bands by regulation
Channel structure within this bands - using of a selected /negotiated channels for the whole transmission
assigned at the beginning of the data exchange
Basic stepsFinding the partner mostly by beaconing (notably base stations!)
Exchanging set-up data separate signaling channel or in-band
Selecting a channel to work on ditto
TKN Telecommunication Networks Group 54
What does change in CR ? (potentially) Usage of arbitrary frequency ranges (for much
better spectrum utilization) Approach: Consulting data basis + distributed sensing
No fixed channel structure (for flexible adaptation to the traffic needs…)
Approach: Negotiating variable channel structure
Imposed high dynamics in changing the used frequencies (if the primary user pops-up!)
Approach: sense while communicating (how?)
Usage of arbitrary transmission schemataApproach: Use OFDMA (see 802.22)
TKN Telecommunication Networks Group 55
Looks like a revolution? Not entirely…
Usage of specific frequency bands ?GSM: 900/1800/1900 ….
IEEE 802.11: 2.4GHz, 5.4 GHz, 5.9 GHZ (DSRC)…
WiMAX…
Specialized transmission schemata? General trend towards OFDM /OFDMA!!!
Exclusive usage of frequency bands? Take 802.11 ….
Coexistence with radars (in 5 GHZ/Europe), microwave ovens, Bluetooth, 802.15.4, etc
Persistent usage of assigned channel?Some frequency hopping during the communication (802.11 FH, Bluetooth, Some GSM)
Channel change in 802.11 (e.g. Mobility…)
TKN Telecommunication Networks Group 56
Lessons learned:
There is a trend to increase the dynamics of adaptive resource usage on each time scale and granularity.
OFDMA seems to be especially attractive transmission schema
Available systems/set-ups allow for investigation of multiple features for the future “Cognitive Radio”
TKN Telecommunication Networks Group 57
Thank You !
TKN Telecommunication Networks Group 58
IEEE 802.15.4a Chirp … some facts [www.nanotron.com]
Chirp technology operating in 2.4 GHz ISM band, 20 MHz, 7 channels (3 non overlapping)
Data rates 2, 1 Mbps; 500, 250, 125, 62.5, 31.25 kbps
Power/sensitivityTx: up o dBm (plus ext. amplifier for long range)
Rx: -97dBm @ 250kbps; BER= 10-3 (with FEC)
Symmetrical double-sided two way ranging
128 bit hardware encryption.
RS 232 interface (USB expected…)
TKN Telecommunication Networks Group 59
IEEE 802.15.4a Chirp … early data [IEEE Documents]
Indoor (European office building) measurement results for a data rate of 1 Mbps (over air interface) and BER = 0.001 are as follows:
Output power (EIRP) = -30 dBm (1 µW), distance = 5 m, 1 wall
Output power (EIRP) = -15 dBm (32 µW), distance = 23 m, 4 walls
Outdoor measurement results for a data rate of 1 Mbps (over air interface) and BER = 0.001 are as follows:
Output power (EIRP) = +7 dBm (5 mW), distance = 739 m (+/-10 m)
Both transceivers use equivalent isotropic antenna (gain = 0 dBi)
For long ranges the transmit power may be allowed to rise to each country’s regulatory limit
For example the US would allow 30 dBm of output power with up to a 6 dB gain antenna
The European ETS limits would specify 20 dBm of output power with a 0 dB gain antenna
Ranging: 2m indoors – 1 m outdoors…. (data sheet)
TKN Telecommunication Networks Group 60
Communication Stack
Secondary users create communicating GROUPS (SUGs)
A universal control channel as well as group control channels are assumed...
PHYLayer
LinkLayer
UCC GCC Data Transfer Channel
SpectrumSensing
ChannelEstimation
Data Transmission
MAC
Group ManagementLink Management
DataTransmission
DataTransmission
MACMAC
Control channels....
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