[SPARK] 安裝 SPARK 1.6.1 測試環境

作者： -
在Spark的介紹中,
我們可以看到Spark的相關的專案:

Spark runs on Java 7+, Python 2.6+ and R 3.1+. For the Scala API, Spark 1.6.1 uses Scala 2.10. You will need to use a compatible Scala version (2.10.x).

其中, 需要預先安裝的元件包括:
Java (1.7版本以上)
Scala (2.10版本以上)

在這一篇文章中, 將在ubuntu 16.02上安裝spark的測試環境,

一開始, 我們先安裝java 1.7的版本:

$ sudo apt-add-repository ppa:webupd8team/java
$ sudo apt-get update
$ sudo apt-get install oracle-java7-installer
安裝完後, 透過指令, 我們可以看到現在安裝的java version:

$ java -version
java version "1.7.0_80"
Java(TM) SE Runtime Environment (build 1.7.0_80-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)
接著, 我們去安裝Scala 2.10.4的版本,

$ wget http://www.scala-lang.org/files/archive/scala-2.10.4.tgz
$ sudo mkdir /usr/local/src/scala
$ sudo tar xvf scala-2.10.4.tgz -C /usr/local/src/scala/
解壓縮完scala後, 我們要設定.bashrc中的scala路徑,
.bashrc是個人環境變數設定檔,
用來設定在該環境下的環境變數...

$ vi .bashrc
把以下的內容補充在.bashrc下方:

# SCALA
export SCALA_HOME=/usr/local/src/scala/scala-2.10.4
export PATH=$SCALA_HOME/bin:$PATH
透過以下指令, 我們可以確認scala的版本:

$ scala -version
Scala code runner version 2.10.4 -- Copyright 2002-2013, LAMP/EPFL
接著, 我們安裝GIT環境,

$ sudo apt-get install git
並且接下來下載spark 1.6.1的版本並解壓縮spark 1.6.1,

$ wget http://ftp.twaren.net/Unix/Web/apache/spark/spark-1.6.1/spark-1.6.1.tgz
$ tar xvf spark-1.6.1.tgz
透過SBT(Simple Build Tool), 我們接著編譯spark的環境

$ cd spark-1.6.1
$ sbt/sbt assembly
接下來, 會跑上許多時間...
根據跑出來的log與info資訊,
在此編譯過程中, 會下載hadoop, maven等相關元件,
不過, 有許多warning和error訊息,
這一部分應該要trace一下在SBT的安裝過程到底會抓取那些元件,
如果有更多資訊, 會在之後的文章補充...

在經過一段時間等候後,
我們可以用以下範例測試spark,

./bin/run-example SparkPi 10
以下是執行後的結果:

ubuntu@spark:~/spark-1.6.1$ ./bin/run-example SparkPi 10
Using Spark's default log4j profile: org/apache/spark/log4j-defaults.properties
16/06/01 11:44:06 INFO SparkContext: Running Spark version 1.6.1
16/06/01 11:44:08 WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
16/06/01 11:44:09 INFO SecurityManager: Changing view acls to: ubuntu
16/06/01 11:44:09 INFO SecurityManager: Changing modify acls to: ubuntu
16/06/01 11:44:09 INFO SecurityManager: SecurityManager: authentication disabled; ui acls disabled; users with view permissions: Set(ubuntu); users with modify permissions: Set(ubuntu)
16/06/01 11:44:11 INFO Utils: Successfully started service 'sparkDriver' on port 40120.
16/06/01 11:44:13 INFO Slf4jLogger: Slf4jLogger started
16/06/01 11:44:13 INFO Remoting: Starting remoting
16/06/01 11:44:13 INFO Remoting: Remoting started; listening on addresses :[akka.tcp://sparkDriverActorSystem@192.168.144.26:48032]
16/06/01 11:44:13 INFO Utils: Successfully started service 'sparkDriverActorSystem' on port 48032.
16/06/01 11:44:13 INFO SparkEnv: Registering MapOutputTracker
16/06/01 11:44:13 INFO SparkEnv: Registering BlockManagerMaster
16/06/01 11:44:13 INFO DiskBlockManager: Created local directory at /tmp/blockmgr-5e1eaf89-3adc-4ebc-915b-3f9683568b34
16/06/01 11:44:14 INFO MemoryStore: MemoryStore started with capacity 511.5 MB
16/06/01 11:44:14 INFO SparkEnv: Registering OutputCommitCoordinator
16/06/01 11:44:14 INFO Server: jetty-8.y.z-SNAPSHOT
16/06/01 11:44:14 INFO AbstractConnector: Started SelectChannelConnector@0.0.0.0:4040
16/06/01 11:44:14 INFO Utils: Successfully started service 'SparkUI' on port 4040.
16/06/01 11:44:14 INFO SparkUI: Started SparkUI at http://192.168.144.26:4040
16/06/01 11:44:14 INFO HttpFileServer: HTTP File server directory is /tmp/spark-e250b06e-9683-45d4-bab1-0f74970e5a4f/httpd-820fd134-dc09-4f6f-9dc5-4fa476a2c3e1
16/06/01 11:44:14 INFO HttpServer: Starting HTTP Server
16/06/01 11:44:15 INFO Server: jetty-8.y.z-SNAPSHOT
16/06/01 11:44:15 INFO AbstractConnector: Started SocketConnector@0.0.0.0:57708
16/06/01 11:44:15 INFO Utils: Successfully started service 'HTTP file server' on port 57708.
16/06/01 11:44:20 INFO SparkContext: Added JAR file:/home/ubuntu/spark-1.6.1/examples/target/scala-2.10/spark-examples-1.6.1-hadoop2.2.0.jar at http://192.168.144.26:57708/jars/spark-examples-1.6.1-hadoop2.2.0.jar with timestamp 1464781460113
16/06/01 11:44:20 INFO Executor: Starting executor ID driver on host localhost
16/06/01 11:44:20 INFO Utils: Successfully started service 'org.apache.spark.network.netty.NettyBlockTransferService' on port 51943.
16/06/01 11:44:20 INFO NettyBlockTransferService: Server created on 51943
16/06/01 11:44:20 INFO BlockManagerMaster: Trying to register BlockManager
16/06/01 11:44:20 INFO BlockManagerMasterEndpoint: Registering block manager localhost:51943 with 511.5 MB RAM, BlockManagerId(driver, localhost, 51943)
16/06/01 11:44:20 INFO BlockManagerMaster: Registered BlockManager
16/06/01 11:44:25 INFO SparkContext: Starting job: reduce at SparkPi.scala:36
16/06/01 11:44:27 INFO DAGScheduler: Got job 0 (reduce at SparkPi.scala:36) with 10 output partitions
16/06/01 11:44:27 INFO DAGScheduler: Final stage: ResultStage 0 (reduce at SparkPi.scala:36)
16/06/01 11:44:27 INFO DAGScheduler: Parents of final stage: List()
16/06/01 11:44:27 INFO DAGScheduler: Missing parents: List()
16/06/01 11:44:27 INFO DAGScheduler: Submitting ResultStage 0 (MapPartitionsRDD[1] at map at SparkPi.scala:32), which has no missing parents
16/06/01 11:44:28 INFO MemoryStore: Block broadcast_0 stored as values in memory (estimated size 1904.0 B, free 1904.0 B)
16/06/01 11:44:28 INFO MemoryStore: Block broadcast_0_piece0 stored as bytes in memory (estimated size 1218.0 B, free 3.0 KB)
16/06/01 11:44:28 INFO BlockManagerInfo: Added broadcast_0_piece0 in memory on localhost:51943 (size: 1218.0 B, free: 511.5 MB)
16/06/01 11:44:28 INFO SparkContext: Created broadcast 0 from broadcast at DAGScheduler.scala:1006
16/06/01 11:44:28 INFO DAGScheduler: Submitting 10 missing tasks from ResultStage 0 (MapPartitionsRDD[1] at map at SparkPi.scala:32)
16/06/01 11:44:28 INFO TaskSchedulerImpl: Adding task set 0.0 with 10 tasks
16/06/01 11:44:28 INFO TaskSetManager: Starting task 0.0 in stage 0.0 (TID 0, localhost, partition 0,PROCESS_LOCAL, 2157 bytes)
16/06/01 11:44:28 INFO TaskSetManager: Starting task 1.0 in stage 0.0 (TID 1, localhost, partition 1,PROCESS_LOCAL, 2157 bytes)
16/06/01 11:44:28 INFO TaskSetManager: Starting task 2.0 in stage 0.0 (TID 2, localhost, partition 2,PROCESS_LOCAL, 2157 bytes)
16/06/01 11:44:28 INFO TaskSetManager: Starting task 3.0 in stage 0.0 (TID 3, localhost, partition 3,PROCESS_LOCAL, 2157 bytes)
16/06/01 11:44:28 INFO Executor: Running task 3.0 in stage 0.0 (TID 3)
16/06/01 11:44:28 INFO Executor: Running task 2.0 in stage 0.0 (TID 2)
16/06/01 11:44:28 INFO Executor: Running task 0.0 in stage 0.0 (TID 0)
16/06/01 11:44:28 INFO Executor: Running task 1.0 in stage 0.0 (TID 1)
16/06/01 11:44:28 INFO Executor: Fetching http://192.168.144.26:57708/jars/spark-examples-1.6.1-hadoop2.2.0.jar with timestamp 1464781460113
16/06/01 11:44:28 INFO Utils: Fetching http://192.168.144.26:57708/jars/spark-examples-1.6.1-hadoop2.2.0.jar to /tmp/spark-e250b06e-9683-45d4-bab1-0f74970e5a4f/userFiles-23014585-18b5-4cde-8bd3-170edab487e9/fetchFileTemp7405909665703120277.tmp
16/06/01 11:44:37 INFO Executor: Adding file:/tmp/spark-e250b06e-9683-45d4-bab1-0f74970e5a4f/userFiles-23014585-18b5-4cde-8bd3-170edab487e9/spark-examples-1.6.1-hadoop2.2.0.jar to class loader
16/06/01 11:44:37 INFO Executor: Finished task 0.0 in stage 0.0 (TID 0). 1031 bytes result sent to driver
16/06/01 11:44:37 INFO Executor: Finished task 3.0 in stage 0.0 (TID 3). 1031 bytes result sent to driver
16/06/01 11:44:37 INFO TaskSetManager: Starting task 4.0 in stage 0.0 (TID 4, localhost, partition 4,PROCESS_LOCAL, 2157 bytes)
16/06/01 11:44:37 INFO Executor: Running task 4.0 in stage 0.0 (TID 4)
16/06/01 11:44:37 INFO TaskSetManager: Starting task 5.0 in stage 0.0 (TID 5, localhost, partition 5,PROCESS_LOCAL, 2157 bytes)
16/06/01 11:44:37 INFO Executor: Running task 5.0 in stage 0.0 (TID 5)
16/06/01 11:44:37 INFO Executor: Finished task 2.0 in stage 0.0 (TID 2). 1031 bytes result sent to driver
16/06/01 11:44:37 INFO TaskSetManager: Finished task 0.0 in stage 0.0 (TID 0) in 9013 ms on localhost (1/10)
16/06/01 11:44:37 INFO TaskSetManager: Starting task 6.0 in stage 0.0 (TID 6, localhost, partition 6,PROCESS_LOCAL, 2157 bytes)
16/06/01 11:44:37 INFO Executor: Finished task 1.0 in stage 0.0 (TID 1). 1031 bytes result sent to driver
16/06/01 11:44:37 INFO TaskSetManager: Finished task 3.0 in stage 0.0 (TID 3) in 8930 ms on localhost (2/10)
16/06/01 11:44:37 INFO Executor: Running task 6.0 in stage 0.0 (TID 6)
16/06/01 11:44:37 INFO TaskSetManager: Starting task 7.0 in stage 0.0 (TID 7, localhost, partition 7,PROCESS_LOCAL, 2157 bytes)
16/06/01 11:44:37 INFO Executor: Running task 7.0 in stage 0.0 (TID 7)
16/06/01 11:44:37 INFO TaskSetManager: Finished task 2.0 in stage 0.0 (TID 2) in 8952 ms on localhost (3/10)
16/06/01 11:44:37 INFO TaskSetManager: Finished task 1.0 in stage 0.0 (TID 1) in 8958 ms on localhost (4/10)
16/06/01 11:44:37 INFO Executor: Finished task 4.0 in stage 0.0 (TID 4). 1031 bytes result sent to driver
16/06/01 11:44:37 INFO TaskSetManager: Starting task 8.0 in stage 0.0 (TID 8, localhost, partition 8,PROCESS_LOCAL, 2157 bytes)
16/06/01 11:44:37 INFO Executor: Running task 8.0 in stage 0.0 (TID 8)
16/06/01 11:44:37 INFO TaskSetManager: Finished task 4.0 in stage 0.0 (TID 4) in 162 ms on localhost (5/10)
16/06/01 11:44:37 INFO Executor: Finished task 6.0 in stage 0.0 (TID 6). 1031 bytes result sent to driver
16/06/01 11:44:37 INFO TaskSetManager: Starting task 9.0 in stage 0.0 (TID 9, localhost, partition 9,PROCESS_LOCAL, 2157 bytes)
16/06/01 11:44:37 INFO TaskSetManager: Finished task 6.0 in stage 0.0 (TID 6) in 277 ms on localhost (6/10)
16/06/01 11:44:37 INFO Executor: Running task 9.0 in stage 0.0 (TID 9)
16/06/01 11:44:37 INFO Executor: Finished task 7.0 in stage 0.0 (TID 7). 1031 bytes result sent to driver
16/06/01 11:44:37 INFO TaskSetManager: Finished task 7.0 in stage 0.0 (TID 7) in 314 ms on localhost (7/10)
16/06/01 11:44:37 INFO Executor: Finished task 5.0 in stage 0.0 (TID 5). 1031 bytes result sent to driver
16/06/01 11:44:37 INFO TaskSetManager: Finished task 5.0 in stage 0.0 (TID 5) in 394 ms on localhost (8/10)
16/06/01 11:44:37 INFO Executor: Finished task 8.0 in stage 0.0 (TID 8). 1031 bytes result sent to driver
16/06/01 11:44:37 INFO TaskSetManager: Finished task 8.0 in stage 0.0 (TID 8) in 284 ms on localhost (9/10)
16/06/01 11:44:37 INFO Executor: Finished task 9.0 in stage 0.0 (TID 9). 1031 bytes result sent to driver
16/06/01 11:44:37 INFO TaskSetManager: Finished task 9.0 in stage 0.0 (TID 9) in 139 ms on localhost (10/10)
16/06/01 11:44:37 INFO DAGScheduler: ResultStage 0 (reduce at SparkPi.scala:36) finished in 9.477 s
16/06/01 11:44:37 INFO TaskSchedulerImpl: Removed TaskSet 0.0, whose tasks have all completed, from pool
16/06/01 11:44:37 INFO DAGScheduler: Job 0 finished: reduce at SparkPi.scala:36, took 12.426088 s
Pi is roughly 3.142784
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/metrics/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/stages/stage/kill,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/api,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/static,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/executors/threadDump/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/executors/threadDump,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/executors/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/executors,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/environment/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/environment,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/storage/rdd/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/storage/rdd,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/storage/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/storage,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/stages/pool/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/stages/pool,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/stages/stage/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/stages/stage,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/stages/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/stages,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/jobs/job/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/jobs/job,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/jobs/json,null}
16/06/01 11:44:37 INFO ContextHandler: stopped o.e.j.s.ServletContextHandler{/jobs,null}
16/06/01 11:44:38 INFO SparkUI: Stopped Spark web UI at http://192.168.144.26:4040
16/06/01 11:44:38 INFO MapOutputTrackerMasterEndpoint: MapOutputTrackerMasterEndpoint stopped!
16/06/01 11:44:38 INFO MemoryStore: MemoryStore cleared
16/06/01 11:44:38 INFO BlockManager: BlockManager stopped
16/06/01 11:44:38 INFO BlockManagerMaster: BlockManagerMaster stopped
16/06/01 11:44:38 INFO OutputCommitCoordinator$OutputCommitCoordinatorEndpoint: OutputCommitCoordinator stopped!
16/06/01 11:44:38 INFO RemoteActorRefProvider$RemotingTerminator: Shutting down remote daemon.
16/06/01 11:44:38 INFO RemoteActorRefProvider$RemotingTerminator: Remote daemon shut down; proceeding with flushing remote transports.
16/06/01 11:44:38 INFO SparkContext: Successfully stopped SparkContext
16/06/01 11:44:38 INFO ShutdownHookManager: Shutdown hook called
16/06/01 11:44:38 INFO ShutdownHookManager: Deleting directory /tmp/spark-e250b06e-9683-45d4-bab1-0f74970e5a4f
16/06/01 11:44:38 INFO RemoteActorRefProvider$RemotingTerminator: Remoting shut down.
16/06/01 11:44:38 INFO ShutdownHookManager: Deleting directory /tmp/spark-e250b06e-9683-45d4-bab1-0f74970e5a4f/httpd-820fd134-dc09-4f6f-9dc5-4fa476a2c3e1

參考資料:
http://blog.prabeeshk.com/blog/2014/10/31/install-apache-spark-on-ubuntu-14-dot-04/
https://spark.apache.org/downloads.html
http://www.apache.org/dyn/closer.lua/spark/spark-1.6.1/spark-1.6.1.tgz

留言

張貼留言

熱門文章

LTE筆記: RSRP, RSSI and RSRQ

作者： -
圖片
在一般通訊系統中, 我們常用 RSSI (Received Signal Strength Indication) 來表示訊號強度,  其單位為 (dBm), 可以轉換成功率大小 (mW): https://en.wikipedia.org/wiki/DBm [註] dBm 的原意即是: (dB) reference to (m)W, 因此, 1 W = 10*log10(1000mW) = 30dBm. 在 LTE 通訊系統中, 除了 RSSI 之外, 又額外定義了兩個用以標示訊號強度的數值: RSRP 和 RSRQ 以下, 我們將介紹 RSRP, RSRQ 和 RSSI 的不同： Reference Symbol Received Power (RSRP) RSRP 為 UE 量測 Reference Signals (RS) 的平均訊號強度, DRS 為基地台在下行訊號中, 於固定 RB (Resource Block) 上傳送的訊號, 由於這些訊號具有特定的傳送格式, 接收端便可以解出這些控制訊號的強度, 對於不同的相鄰基地台, 甚至是同一基地台不同的天線, 可以透過不同的 RS 配置, 讓使用者得知不同目標的量測數值, 如下圖所示: 紅色為 RS, 不同基地台或天線使用不同的 RS 排列方法, 可分開量測 來自: https://api.semanticscholar.org/CorpusID:22030582 RSRP 的回報由 UE 進行 Measurement Report, 回傳給基地台, 其中, 關於 Measurement Report 的設置定義於 RRC 的規範中, 我們之後有機會再提, RSRP 的量測, 通常在換手 (handover) 時進行量測, 用以指出目標基地台的訊號強度, 其中, UE 所量測的數值, 將藉由下表進行轉換 (訊號強度 (dBm) - (-140)), 並回報給 eNB 作為換手的決策使用: (3GPP Reference: TS 36.133) RSSI (Received Signal Strength Indication)  RSSI 是 UE 接收到的 wide-band 訊號強度, 包含 DRS 以及其他 RB 的訊號強度 (第一張
閱讀完整內容

[WiFi] WiFi 網路的識別: BSS, ESS, SSID, ESSID, BSSID

作者： -
圖片
在 WiFi 網路中, 一個基本的識別方式就是 SSID (Service Set Identifier), 也就是我們口語中的 "WiFi 網路名稱", 然而, 此網路事實上是一個服務集合 (Service Set) 的概念, 而一個服務群集, 也可以對應到一個基本的無線網路, 包含: 一個 WiFi AP 以及多個 WiFi 使用者, 對於剛剛這種簡單的網路架構, 又稱為 BSS (Basic Service Set), 若是多個 BSS 都使用同一個 SSID, 則稱為 ESS (Extend Service Set), 如下圖所示: 來自: https://ppt.cc/fXIvex 對於 ESS 來說, 有兩個假設, 第一, 底下的 BSS 必須是相鄰 (有交疊範圍) 第二, 這些 BSS 有網路連線, (有線或是無線都可以) 這兩個假設是為了完成 ESS 的主要功能, 也就是換手 (handoff), 當裝置在同一個 ESS 下不同 BSS 範圍中移動時, 可不必重新連線就可以繼續傳輸. 這樣的流程事實上是由原本服務的 AP (BSS 1), 把使用者的資料轉傳到換手目標的 AP (BSS 2), 資料流程為: DS -> BSS 1 -> BSS 2 -> Sation, 也因此, 兩個 AP 之間必須連線, 同時切換時間也不能太久 (相鄰條件), 那麼在上述例子中, 如何知道 BSS 1 和 BSS 2 的差別呢? 在 WiFi 網路中, 為了完成這件事情, 所以就有了 ESSID 和 BSSID, ESSID 如上所述, 對應於 ESS 所使用的 SSID, 至於 BSSID (通常是 WiFi AP 的 MAC 位址) 來區分同個 SSID 下的網路. 反過來說, 同一個 WiFi AP 也可以擁有多個 SSID, 此功能稱為 VAP (Virtual AP), 此時, 一個 WiFi AP 會虛擬出多個 BSSID, 通常作法就是從原有的 MAC 位址往上加一, 作為多個不同的 BSSID. 這些 VAP 會對應到 WiFi AP 中的不同 VLAN 中, 因此, 我們可以給他們不同的網路設定, 例如: 流量, 安全性, 頻寬等,
閱讀完整內容

LTE筆記: 波束成型 (beamforming) 和天線陣列

作者： -
圖片
在5G的技術中, 其中一個新被引入的通訊技術就是波束成型 (beamforming), 波束成型技術可以大略的分成兩種: 第一種、藉由量測到的通道係數, 設計傳送參數 (precoder), 最佳化通道 第二種、透過多天線的相位偏移 (phase shifter), 決定電波傳遞強度模 在文章中, 會著重介紹第二種波束成型的架構, 在第二種波束成型的架構中, 所使用的是電磁波干射的物理特性, 簡單來說, 透過電磁波的建設性干涉與破壞性干涉, 我們就可以在某個方向上產生一個較強的訊號, 而在其他方向上減低此訊號的影響. 來自:  https://en.wikipedia.org/wiki/Phased_array 在上圖中, 我們可以發現這種波束成型架構的兩個需求: 1. 必須有多根天線服務同一筆傳輸訊號 2. 每個天線都必須要有一個相位調節器 (phase shifter)
閱讀完整內容