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IEEE 802.15.4 - 非同期 CSMA MAC

この例では、Communications Toolbox™ Library for the ZigBee® Protocol を使用して、IEEE® 802.15.4™ 非同期 CSMA MAC [1] をシミュレーションする方法を説明します。

背景

IEEE 802.15.4 規格は、低速無線パーソナル エリア ネットワーク (LR-WPAN) [1] の MAC 層と PHY 層を規定します。IEEE 802.15.4 の MAC 層と PHY 層は、ZigBee、WirelessHart®、6LoWPAN、MiWi などの他の上位層の規格のベースを提供します。このような規格は、ホーム オートメーションやセンサー ネットワーキングに使用例があり、モノのインターネット (IoT) の流行にも密接に関連しています。

IEEE 802.15.4 MAC [ 1 ] は、2 つの基本的な MAC モード、(i) ビーコン非対応 MAC と (ii) ビーコン対応 MAC を規定します。ビーコン非対応 MAC は非同期 CSMA (Carrier-sense Multiple Access) MAC であり、IEEE 802.11 MAC にとてもよく似ています。ビーコン対応 MAC では、2 つの異なる MAC 周期 (i) 同期型の CSMA MAC 周期と (ii) タイム スロット型の競合のない MAC 周期が許可されます。この例では、ビーコン非対応の非同期 CSMA ベースの IEEE 802.15.4 MAC について幅広いシミュレーションを提供します。

ネットワーク設定

IEEE 802.15.4 PAN (パーソナル エリア ネットワーク) は、エンド デバイスと PAN コーディネーターの間の標準的な処理によって設定されます。はじめに、ネットワークに参加しようとしているデバイスが、アクティブまたはパッシブのスキャンを実行します。アクティブ スキャンとは、デバイスがはじめにビーコン要求を送信し、その後でパッシブ スキャンを実行することです。パッシブ スキャンとは、デバイスが PAN コーディネーターからのビーコン フレームを収集するために監視を行うことです。アクティブ スキャンの場合、PAN コーディネーターはビーコン要求を受信済みであることがあります。パッシブ スキャン中にビーコンを収集しているときに、エンド デバイスが関連付けをする PAN を選択します。その後、アソシエーション要求をこの PAN のコーディネーターに送信し、コーディネーターがその要求に肯定応答します。

IEEE 802.11 とは対照的に、コーディネーターはアソシエーション応答をすぐに送信することでアソシエーション要求の肯定応答をフォローしません。代わりに、IEEE 802.15.4 コーディネーターは初めにアソシエーション応答をローカルに保存し、エンド デバイスがデータ要求を送信しコーディネーターがそれに肯定応答するときにのみ、アソシエーション応答を送信します。IEEE 802.15.4 規格では、このフレーム送信メカニズムを指して間接伝送という用語を使用します。一般に、このメカニズムはトラフィックが少ないネットワーク (センサー ネットワークなど) のバッテリーにより電力を供給されるデバイスにとって非常に有用です。このようなデバイスは、フレームを即座に受信できるように絶え間なく無線を使用する代わりに、定期的に無線をアクティブにして自分宛てのフレームが保留されているかどうかをチェックします。

アソシエーション応答が受信され肯定応答されると、エンド デバイスが PAN に関連付けされます。そうすると、コーディネーターとエンド デバイスの間で双方向にデータ フレームをやり取りできるようになります。データ フレームは、'肯定応答要求' の指示に応じて、肯定応答されます。

非同期メディア アクセス制御 (MAC)

非同期 CSMA IEEE 802.15.4 MAC は、一般的な CSMA の処理と IEEE 802.11 MAC によく似ています。この MAC スキームでは、CSMA の手法を用いず、肯定応答フレームは即座に送信されます。他のすべてのフレームは CSMA を使用して送信されます。

具体的には、デバイスは、送信すべきフレームを持つと、[0 2^BE-1] の範囲からランダムにバックオフ遅延 (バックオフ周期の数) を選択します。ここで BE はバックオフ指数です。各バックオフ周期の期間は 20 シンボルです。2.4 GHz の OQPSK PHY では、この期間は 128 チップと 0.32 ms に相当します。デバイスは、選択したバックオフ周期の数だけ待機すると、搬送波感知を実行します。メディアがアイドルである場合は、デバイスはそのフレームの送信を開始し、すべて送信するまで継続します。

搬送波感知中メディアがビジーであった場合は、バックオフ指数が 1 増やされ、新しい範囲 [0 2^BE-1] から新しいバックオフ周期数が選択されます。再度バックオフ カウンターがいっぱいになったら、搬送波検出が実行されます。すべての搬送波検出インスタンスの間、メディアがアイドルにならずに、バックオフ カウントダウンの最大数に達した場合は、デバイスはフレーム送信試行を終了します。

ネットワーク シミュレーション機能

この例では、lrwpan.MACFullFunctionDevice および lrwpan.MACReducedFunctionDevice クラスを介して、説明したネットワーク設定処理と CSMA 手法を実装します。具体的には、以下の機能が有効にされます。

  • アクティブおよびパッシブ スキャン

  • アソシエーション要求とアソシエーション応答の交換

  • データ要求を使用した間接伝送

  • 肯定応答がタイムリーに受信されない場合のフレーム肯定応答とフレームの再送信

  • 短いフレーム間隔および長いフレーム間隔 (SIFS および LIFS)

  • バイナリ指数バックオフ

  • 搬送波検出

ネットワーク シミュレーション

この節では、3 ノード (1 つの PAN コーディネーターと 2 つのエンド デバイス) で構成される IEEE 802.15.4 ネットワークを作成します。ネットワーク シミュレーターは、単一のバックオフ持続時間 (20 シンボル、0.32 ms) を 1 つずつ増やしてすべてのデバイスを処理するように構成します。

はじめに、次のコードで、最初のデバイスとネットワークの関連付けを示します。

symbolsPerStep = 20;
chipsPerSymbol = 32;
samplesPerChip = 4;
symbolRate = 65.5e3; % symbols/sec
time = 0;
stopTime = 5; % sec

% Create PAN Coordinator
panCoordinator = lrwpan.MACFullFunctionDevice('PANCoordinator', true, 'SamplesPerChip', 4, ....
  'PANIdentifier', '7777', 'ExtendedAddress', [repmat('0', 1, 8) repmat('7', 1, 8)], ...
  'ShortAddress', '1234');

% Create first end-device:
endDevice1 = lrwpan.MACReducedFunctionDevice('SamplesPerChip', 4, ...
  'ShortAddress', '0001', 'ExtendedAddress', [repmat('0', 1, 8) repmat('3', 1, 8)]);

% Initialize device inputs
received1 = zeros(samplesPerChip * chipsPerSymbol * symbolsPerStep/2, 1);
received2 = zeros(samplesPerChip * chipsPerSymbol * symbolsPerStep/2, 1);

while time < stopTime
  % Pass the received signals to the nodes for processing. Also, fetch what
  % they have to transmit:
  transmitted1 = panCoordinator(received1);
  transmitted2 = endDevice1(received2);

  % Ideal wireless channel, where both nodes are within range:
  received1 = transmitted2; % half-duplex radios, none receiving while transmitting
  received2 = transmitted1;

  time = time + symbolsPerStep/symbolRate; % update clock
end
0001: ********* Adding Beacon Request frame to the queue
0001: Passive scanning for 1584 steps
0001: Processing next frame from the queue
0001: Initializing transmission; backoff delay = 1 steps
0001: Backoff delay = 1 steps -> 0 steps
0001: Carrier sensing: Medium is idle.
0001: Clear to transmit
0001: Transmitting Beacon Request
0001: IFS offset = 0 samples
0001: Transmitting 1-1280 of 2050
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
0001: IFS offset = 0 samples
0001: Transmitting 1281-2050 of 2050
0001: Finished transmission
0001: Need to wait for SIFS (12) symbols. Offset = 12, next IFS = 4
0001: Entering passive scanning
1234: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
1234: *********** Received frame type = MAC command
1234: *********** Received MAC Command type = Beacon request
1234: Need to wait for SIFS (12) symbols. Offset = 12, next IFS = 4
1234: ********* Adding Beacon frame to the queue
1234: next IFS = 4
1234: Processing next frame from the queue
1234: Initializing transmission; backoff delay = 7 steps
1234: Backoff delay = 7 steps -> 6 steps
1234: Backoff delay = 6 steps -> 5 steps
1234: Backoff delay = 5 steps -> 4 steps
1234: Backoff delay = 4 steps -> 3 steps
1234: Backoff delay = 3 steps -> 2 steps
1234: Backoff delay = 2 steps -> 1 steps
1234: Backoff delay = 1 steps -> 0 steps
1234: Carrier sensing: Medium is idle.
1234: Clear to transmit
1234: IFS offset = 256 samples
1234: Transmitting 1-1024 of 2562
1234: IFS offset = 0 samples
1234: Transmitting 1025-2304 of 2562
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
1234: IFS offset = 0 samples
1234: Transmitting 2305-2562 of 2562
1234: Finished transmission
1234: Need to wait for LIFS (40) symbols. Offset = 4, next IFS = 24
1234: Decreased wait time by 20 symbols to 4
0001: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
0001: *********** Received frame type = Beacon
0001: Need to wait for SIFS (12) symbols. Offset = 4, next IFS = -4
0001: next IFS = 0
0001: Scanning finished
0001: ********* Adding Association request frame to the queue
0001: Processing next frame from the queue
0001: Initializing transmission; backoff delay = 0 steps
0001: Carrier sensing: Medium is idle.
0001: Clear to transmit
0001: IFS offset = 0 samples
0001: Transmitting 1-1280 of 3458
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
0001: IFS offset = 0 samples
0001: Transmitting 1281-2560 of 3458
0001: IFS offset = 0 samples
0001: Transmitting 2561-3458 of 3458
0001: Finished transmission
0001: will wait for ack for 54 symbols additional to IFS = 0
1234: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
1234: *********** Received frame type = MAC command
1234: *********** Received MAC Command type = Association request
1234: Need to wait for LIFS (40) symbols. Offset = 14, next IFS = 34
1234: ********** Directly transmitting acknowledgement frame (no CSMA/CA)
1234: ********* Adding Data response frame to the PENDING queue
1234: next IFS = 34
0001: Decreasing ack wait durations by 20 symbols to 34
1234: IFS offset = 896 samples
1234: Transmitting 1-384 of 1410
0001: Decreasing ack wait durations by 20 symbols to 14
1234: IFS offset = 0 samples
1234: Transmitting 385-1410 of 1410
1234: Finished transmission
1234: Need to wait for SIFS (12) symbols. Offset = 16, next IFS = 8
0001: Decreasing ack wait durations by 20 symbols to -6
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
0001: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
0001: *********** Received frame type = Acknowledgment
0001: Need to wait for SIFS (12) symbols. Offset = 16, next IFS = 8
0001: *********** Adding Data request frame to the queue
0001: next IFS = 1920
0001: Decreased wait time by 20 symbols to 1900
0001: Decreased wait time by 20 symbols to 1880
0001: Decreased wait time by 20 symbols to 1860
0001: Decreased wait time by 20 symbols to 1840
0001: Decreased wait time by 20 symbols to 1820
0001: Decreased wait time by 20 symbols to 1800
0001: Decreased wait time by 20 symbols to 1780
0001: Decreased wait time by 20 symbols to 1760
0001: Decreased wait time by 20 symbols to 1740
0001: Decreased wait time by 20 symbols to 1720
0001: Decreased wait time by 20 symbols to 1700
0001: Decreased wait time by 20 symbols to 1680
0001: Decreased wait time by 20 symbols to 1660
0001: Decreased wait time by 20 symbols to 1640
0001: Decreased wait time by 20 symbols to 1620
0001: Decreased wait time by 20 symbols to 1600
0001: Decreased wait time by 20 symbols to 1580
0001: Decreased wait time by 20 symbols to 1560
0001: Decreased wait time by 20 symbols to 1540
0001: Decreased wait time by 20 symbols to 1520
0001: Decreased wait time by 20 symbols to 1500
0001: Decreased wait time by 20 symbols to 1480
0001: Decreased wait time by 20 symbols to 1460
0001: Decreased wait time by 20 symbols to 1440
0001: Decreased wait time by 20 symbols to 1420
0001: Decreased wait time by 20 symbols to 1400
0001: Decreased wait time by 20 symbols to 1380
0001: Decreased wait time by 20 symbols to 1360
0001: Decreased wait time by 20 symbols to 1340
0001: Decreased wait time by 20 symbols to 1320
0001: Decreased wait time by 20 symbols to 1300
0001: Decreased wait time by 20 symbols to 1280
0001: Decreased wait time by 20 symbols to 1260
0001: Decreased wait time by 20 symbols to 1240
0001: Decreased wait time by 20 symbols to 1220
0001: Decreased wait time by 20 symbols to 1200
0001: Decreased wait time by 20 symbols to 1180
0001: Decreased wait time by 20 symbols to 1160
0001: Decreased wait time by 20 symbols to 1140
0001: Decreased wait time by 20 symbols to 1120
0001: Decreased wait time by 20 symbols to 1100
0001: Decreased wait time by 20 symbols to 1080
0001: Decreased wait time by 20 symbols to 1060
0001: Decreased wait time by 20 symbols to 1040
0001: Decreased wait time by 20 symbols to 1020
0001: Decreased wait time by 20 symbols to 1000
0001: Decreased wait time by 20 symbols to 980
0001: Decreased wait time by 20 symbols to 960
0001: Decreased wait time by 20 symbols to 940
0001: Decreased wait time by 20 symbols to 920
0001: Decreased wait time by 20 symbols to 900
0001: Decreased wait time by 20 symbols to 880
0001: Decreased wait time by 20 symbols to 860
0001: Decreased wait time by 20 symbols to 840
0001: Decreased wait time by 20 symbols to 820
0001: Decreased wait time by 20 symbols to 800
0001: Decreased wait time by 20 symbols to 780
0001: Decreased wait time by 20 symbols to 760
0001: Decreased wait time by 20 symbols to 740
0001: Decreased wait time by 20 symbols to 720
0001: Decreased wait time by 20 symbols to 700
0001: Decreased wait time by 20 symbols to 680
0001: Decreased wait time by 20 symbols to 660
0001: Decreased wait time by 20 symbols to 640
0001: Decreased wait time by 20 symbols to 620
0001: Decreased wait time by 20 symbols to 600
0001: Decreased wait time by 20 symbols to 580
0001: Decreased wait time by 20 symbols to 560
0001: Decreased wait time by 20 symbols to 540
0001: Decreased wait time by 20 symbols to 520
0001: Decreased wait time by 20 symbols to 500
0001: Decreased wait time by 20 symbols to 480
0001: Decreased wait time by 20 symbols to 460
0001: Decreased wait time by 20 symbols to 440
0001: Decreased wait time by 20 symbols to 420
0001: Decreased wait time by 20 symbols to 400
0001: Decreased wait time by 20 symbols to 380
0001: Decreased wait time by 20 symbols to 360
0001: Decreased wait time by 20 symbols to 340
0001: Decreased wait time by 20 symbols to 320
0001: Decreased wait time by 20 symbols to 300
0001: Decreased wait time by 20 symbols to 280
0001: Decreased wait time by 20 symbols to 260
0001: Decreased wait time by 20 symbols to 240
0001: Decreased wait time by 20 symbols to 220
0001: Decreased wait time by 20 symbols to 200
0001: Decreased wait time by 20 symbols to 180
0001: Decreased wait time by 20 symbols to 160
0001: Decreased wait time by 20 symbols to 140
0001: Decreased wait time by 20 symbols to 120
0001: Decreased wait time by 20 symbols to 100
0001: Decreased wait time by 20 symbols to 80
0001: Decreased wait time by 20 symbols to 60
0001: Decreased wait time by 20 symbols to 40
0001: Decreased wait time by 20 symbols to 20
0001: Decreased wait time by 20 symbols to 0
0001: Processing next frame from the queue
0001: Initializing transmission; backoff delay = 2 steps
0001: Backoff delay = 2 steps -> 1 steps
0001: Backoff delay = 1 steps -> 0 steps
0001: Carrier sensing: Medium is idle.
0001: Clear to transmit
0001: IFS offset = 0 samples
0001: Transmitting 1-1280 of 3074
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
0001: IFS offset = 0 samples
0001: Transmitting 1281-2560 of 3074
0001: IFS offset = 0 samples
0001: Transmitting 2561-3074 of 3074
0001: Finished transmission
0001: will wait for ack for 54 symbols additional to IFS = 0
1234: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
1234: *********** Received frame type = MAC command
1234: *********** Received MAC Command type = Data request
1234: Need to wait for SIFS (12) symbols. Offset = 8, next IFS = 0
1234: ********** Directly transmitting acknowledgement frame (no CSMA/CA)
1234: Moving frame for 0000000033333333 from pending queue to the transmission queue
1234: next IFS = 0
1234: IFS offset = 0 samples
1234: Transmitting 1-1280 of 1410
0001: Decreasing ack wait durations by 20 symbols to 34
1234: IFS offset = 0 samples
1234: Transmitting 1281-1410 of 1410
1234: Finished transmission
1234: Need to wait for SIFS (12) symbols. Offset = 2, next IFS = -6
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
0001: Decreasing ack wait durations by 20 symbols to 14
1234: Processing next frame from the queue
1234: Initializing transmission; backoff delay = 5 steps
1234: Backoff delay = 5 steps -> 4 steps
0001: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
0001: *********** Received frame type = Acknowledgment
0001: Need to wait for SIFS (12) symbols. Offset = 2, next IFS = -6
0001: next IFS = 0
1234: Backoff delay = 4 steps -> 3 steps
1234: Backoff delay = 3 steps -> 2 steps
1234: Backoff delay = 2 steps -> 1 steps
1234: Backoff delay = 1 steps -> 0 steps
1234: Carrier sensing: Medium is idle.
1234: Clear to transmit
1234: IFS offset = 0 samples
1234: Transmitting 1-1280 of 4226
1234: IFS offset = 0 samples
1234: Transmitting 1281-2560 of 4226
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
1234: IFS offset = 0 samples
1234: Transmitting 2561-3840 of 4226
1234: IFS offset = 0 samples
1234: Transmitting 3841-4226 of 4226
1234: Finished transmission
1234: will wait for ack for 54 symbols additional to IFS = 0
1234: Decreasing ack wait durations by 20 symbols to 34
0001: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
0001: *********** Received frame type = MAC command
0001: *********** Received MAC Command type = Association response
0001: Need to wait for LIFS (40) symbols. Offset = 6, next IFS = 26
0001: *********** Association successful, changing short address to = 8CEC
8CEC: *********** Association successful, associated to PAN = 7777
8CEC: ********** Directly transmitting acknowledgement frame (no CSMA/CA)
8CEC: next IFS = 26
1234: Decreasing ack wait durations by 20 symbols to 14
8CEC: IFS offset = 384 samples
8CEC: Transmitting 1-896 of 1410
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
1234: Decreasing ack wait durations by 20 symbols to -6
8CEC: IFS offset = 0 samples
8CEC: Transmitting 897-1410 of 1410
8CEC: Finished transmission
8CEC: Need to wait for SIFS (12) symbols. Offset = 8, next IFS = 0
1234: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
1234: *********** Received frame type = Acknowledgment
1234: Need to wait for SIFS (12) symbols. Offset = 8, next IFS = 0
1234: next IFS = 0
8CEC: ********* (t=4.079360) Injecting data frame to the queue. From: 8CEC -> To: 1234 
8CEC: Processing next frame from the queue
8CEC: Initializing transmission; backoff delay = 6 steps
8CEC: Backoff delay = 6 steps -> 5 steps
8CEC: Backoff delay = 5 steps -> 4 steps
8CEC: Backoff delay = 4 steps -> 3 steps
8CEC: Backoff delay = 3 steps -> 2 steps
8CEC: Backoff delay = 2 steps -> 1 steps
8CEC: Backoff delay = 1 steps -> 0 steps
8CEC: Carrier sensing: Medium is idle.
8CEC: Clear to transmit
8CEC: IFS offset = 0 samples
8CEC: Transmitting 1-1280 of 8578
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
8CEC: IFS offset = 0 samples
8CEC: Transmitting 1281-2560 of 8578
8CEC: IFS offset = 0 samples
8CEC: Transmitting 2561-3840 of 8578
8CEC: IFS offset = 0 samples
8CEC: Transmitting 3841-5120 of 8578
8CEC: IFS offset = 0 samples
8CEC: Transmitting 5121-6400 of 8578
8CEC: IFS offset = 0 samples
8CEC: Transmitting 6401-7680 of 8578
8CEC: IFS offset = 0 samples
8CEC: Transmitting 7681-8578 of 8578
8CEC: Finished transmission
8CEC: will wait for ack for 54 symbols additional to IFS = 0
1234: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
1234: *********** Received frame type = Data
1234: Need to wait for SIFS (12) symbols. Offset = 14, next IFS = 6
1234: ********** Directly transmitting acknowledgement frame (no CSMA/CA)
1234: next IFS = 6
1234: IFS offset = 384 samples
1234: Transmitting 1-896 of 1410
8CEC: Decreasing ack wait durations by 20 symbols to 34
1234: IFS offset = 0 samples
1234: Transmitting 897-1410 of 1410
1234: Finished transmission
1234: Need to wait for SIFS (12) symbols. Offset = 8, next IFS = 0
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
8CEC: Decreasing ack wait durations by 20 symbols to 14
8CEC: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
8CEC: *********** Received frame type = Acknowledgment
8CEC: Need to wait for LIFS (40) symbols. Offset = 8, next IFS = 28
8CEC: next IFS = 28
8CEC: Decreased wait time by 20 symbols to 8
8CEC: ********* (t=4.795200) Injecting data frame to the queue. From: 8CEC -> To: 1234 
8CEC: Processing next frame from the queue
8CEC: Initializing transmission; backoff delay = 6 steps
8CEC: Backoff delay = 6 steps -> 5 steps
8CEC: Backoff delay = 5 steps -> 4 steps
8CEC: Backoff delay = 4 steps -> 3 steps
8CEC: Backoff delay = 3 steps -> 2 steps
8CEC: Backoff delay = 2 steps -> 1 steps
8CEC: Backoff delay = 1 steps -> 0 steps
8CEC: Carrier sensing: Medium is idle.
8CEC: Clear to transmit
8CEC: IFS offset = 512 samples
8CEC: Transmitting 1-768 of 8578
Found preamble of OQPSK PHY.
8CEC: IFS offset = 0 samples
8CEC: Transmitting 769-2048 of 8578
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
8CEC: IFS offset = 0 samples
8CEC: Transmitting 2049-3328 of 8578
8CEC: IFS offset = 0 samples
8CEC: Transmitting 3329-4608 of 8578
8CEC: IFS offset = 0 samples
8CEC: Transmitting 4609-5888 of 8578
8CEC: IFS offset = 0 samples
8CEC: Transmitting 5889-7168 of 8578
8CEC: IFS offset = 0 samples
8CEC: Transmitting 7169-8448 of 8578
8CEC: IFS offset = 0 samples
8CEC: Transmitting 8449-8578 of 8578
8CEC: Finished transmission
8CEC: will wait for ack for 54 symbols additional to IFS = 0
1234: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
1234: *********** Received frame type = Data
1234: Need to wait for SIFS (12) symbols. Offset = 2, next IFS = -6
1234: ********** Directly transmitting acknowledgement frame (no CSMA/CA)
1234: next IFS = 0
1234: IFS offset = 0 samples
1234: Transmitting 1-1280 of 1410
8CEC: Decreasing ack wait durations by 20 symbols to 34
1234: IFS offset = 0 samples
1234: Transmitting 1281-1410 of 1410
1234: Finished transmission
1234: Need to wait for SIFS (12) symbols. Offset = 2, next IFS = -6
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
8CEC: Decreasing ack wait durations by 20 symbols to 14
8CEC: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
8CEC: *********** Received frame type = Acknowledgment
8CEC: Need to wait for LIFS (40) symbols. Offset = 2, next IFS = 22
8CEC: next IFS = 22
8CEC: Decreased wait time by 20 symbols to 2
1234: ********* (t=5.001280) Injecting data frame to the queue. From: 1234 -> To: 8CEC 
1234: Processing next frame from the queue
1234: Initializing transmission; backoff delay = 1 steps
1234: Backoff delay = 1 steps -> 0 steps
1234: Carrier sensing: Medium is idle.
1234: Clear to transmit
1234: IFS offset = 0 samples
1234: Transmitting 1-1280 of 8578
1234: IFS offset = 0 samples
1234: Transmitting 1281-2560 of 8578
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
1234: IFS offset = 0 samples
1234: Transmitting 2561-3840 of 8578
1234: IFS offset = 0 samples
1234: Transmitting 3841-5120 of 8578
1234: IFS offset = 0 samples
1234: Transmitting 5121-6400 of 8578
1234: IFS offset = 0 samples
1234: Transmitting 6401-7680 of 8578
1234: IFS offset = 0 samples
1234: Transmitting 7681-8578 of 8578
1234: Finished transmission
1234: will wait for ack for 54 symbols additional to IFS = 0
1234: Decreasing ack wait durations by 20 symbols to 34
8CEC: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
8CEC: *********** Received frame type = Data
8CEC: Need to wait for SIFS (12) symbols. Offset = 14, next IFS = 6
8CEC: ********** Directly transmitting acknowledgement frame (no CSMA/CA)
8CEC: next IFS = 6
8CEC: IFS offset = 384 samples
8CEC: Transmitting 1-896 of 1410
Found preamble of OQPSK PHY.
Found start-of-frame delimiter (SFD) of OQPSK PHY.
1234: Decreasing ack wait durations by 20 symbols to 14
8CEC: IFS offset = 0 samples
8CEC: Transmitting 897-1410 of 1410
8CEC: Finished transmission
8CEC: Need to wait for SIFS (12) symbols. Offset = 8, next IFS = 0
1234: PHY decoded IEEE 802.15.4 frame
CRC check passed for the MAC frame.
1234: *********** Received frame type = Acknowledgment
1234: Need to wait for LIFS (40) symbols. Offset = 8, next IFS = 28
1234: next IFS = 28
1234: Decreased wait time by 20 symbols to 8

1 つ目のエンド デバイスが関連付けられると、エンド デバイスと PAN コーディネーターの間のリンクにデータ フレームがランダムに投入されます。

次に、3 つ目のデバイスが PAN に参加すると、スター トポロジの形で、コーディネーターと両方のエンド デバイス間でデータ フレームが交換されます (エンド デバイスはコーディネーターへのフレーム送信のみを行う必要があります)。この場合出力は表示されません。

% Create second end-device:
endDevice2 = lrwpan.MACReducedFunctionDevice('SamplesPerChip', 4, ...
  'ShortAddress', '0002', 'ExtendedAddress', [repmat('0', 1, 8) repmat('4', 1, 8)], 'Verbosity', false);
% Suppress detailed output:
endDevice1.Verbosity = false;
panCoordinator.Verbosity = false;

% Initialize input
received3 = zeros(samplesPerChip * chipsPerSymbol * symbolsPerStep/2, 1);

stopTime = 10; % sec
while time < stopTime
  % Pass the received signals to the nodes for processing. Also, fetch what
  % they have to transmit:
  transmitted1 = panCoordinator(received1);
  transmitted2 = endDevice1(received2);
  transmitted3 = endDevice2(received3);

  % Ideal wireless channel, where all nodes are within range:
  received1 = transmitted2 + transmitted3; % half-duplex radios, none receiving while transmitting
  received2 = transmitted1 + transmitted3;
  received3 = transmitted1 + transmitted2;

  time = time + symbolsPerStep/symbolRate; % update clock
end

チャネルの関係が適切に確立している (送信された信号に応じて信号が受信される) 限り、ネットワークにはもっとノードを追加できます。

その他の調査

ジェネレーター関数と復号化関数、および構成オブジェクトの詳細については、次の情報を参照してください。

参考文献

  1. IEEE 802.15.4-2011 - IEEE Standard for Local and metropolitan area networks--Part 15.4: Low-Rate Wireless Personal Area Networks (LR-WPANs)