1g到5g各個階段的頻段（從模擬信號到數位訊號）

2023-11-09 12:49:03 2

自從人類了解了電磁波，通信技術的發展也是一波接著一波。

AT&T is scheduled to decommission its 3G cellular network, On February 22, 2022. T-Mobile is scheduled to be shut down on July 1, 2022, and Verizon is set to follow suit on December 31, 2022.

AT&T計劃於2022年2月22日停用其3G蜂窩網絡。T-Mobile計劃於2022年7月1日關閉，Verizon也將於2022年12月31日關閉。

The vast majority of cell phones in the service run on 4G/LTE networks, and the world has begun the transition to 5G, but as many as 10 million phones in the US still rely on 3G service. In addition, the cellular network functionality of some older devices such as Kindles, iPads, and Chromebooks are connected to 3G networks. Similarly, some legacy internet-connected systems such as home security, in-car navigation and entertainment systems, and solar panel modems are for 3G. Consumers will need to upgrade or replace these systems.

該服務中的絕大多數手機都運行在4G/LTE網絡上，世界已經開始向5G過渡，但美國仍有多達1000萬部手機依賴3G服務。此外，Kindle、iPad和Chromebook等舊設備的蜂窩網絡功能也連接到3G網絡。類似地，一些傳統的網際網路連接系統，如家庭安全、車載導航和娛樂系統，以及太陽能電池板數據機也適用於3G。消費者需要升級或更換這些系統。

So why are carriers turning off their 3G networks? As an electrical engineer studying wireless communications, I can explain. The answer starts with the difference between 3G and newer technologies like 4G/LTE and 5G.

那麼，運營商為什麼要關閉3G網絡呢？作為一名研究無線通信的電氣工程師，我可以解釋。答案從3G與4G/LTE和5G等較新技術之間的差異開始。

Imagine a family trip. Your wife is on the phone arranging activities to do at the destination, your teenage daughter is streaming music and talking with her friends on her phone, and her younger brother is playing an online game with his friends. All these separate conversations and data streams are connected over the cellular network, seemingly simultaneously. You might take this for granted, but have you ever wondered how a cellular system can handle all of these activities at the same time, from the same vehicle?

想像一次家庭旅行。你的妻子在電話上安排在目的地的活動，你十幾歲的女兒在流媒體音樂，在手機上和朋友聊天，她的弟弟在和朋友玩網路遊戲。所有這些獨立的對話和數據流似乎同時通過蜂窩網絡連接。你可能會認為這是理所當然的，但你有沒有想過，一個蜂窩系統如何在同一輛車上同時處理所有這些活動？

when everyone in your car is using voice and cellular data at the same time

1 Deliver all those messages 傳遞所有這些信息 （碼分多址 CDMA）

The answer is a technological trick called multiple access. Imagine using a sheet of paper to write letters to 100 different friends, one private message per person. The multiple access technology used in 3G networks is like writing each message to each of your friends using the whole paper, so that all messages are written on top of each other. But you have a special set of pens in different colors that allow you to write each message in a unique color, and each of your friends has a special pair of glasses that reveal only the color assigned to that person.

答案是一種稱為多址接入的技術技巧。想像一下，用一張紙給100個不同的朋友寫信，每人發一條私人信息。3G網絡中使用的多址接入技術就像是用整張紙把每條信息都寫給你的每個朋友，這樣所有的信息都被寫在彼此的上面。但是你有一套不同顏色的特殊鋼筆，可以讓你用一種獨特的顏色寫每條信息，你的每個朋友都有一副特殊的眼鏡，只顯示分配給那個人的顏色。

However, the number of colored pens is fixed, so if you want to send messages to more people than the number of colored pens you have, you will need to start mixing the colors.

然而，彩色筆的數量是固定的，所以如果你想發送信息給更多的人，而不是你擁有的彩色筆的數量，你需要開始混合顏色。

Now when a friend applies his own lenses, he will see few messages to other friends. They won’t see enough to read other messages, but the interference may be enough to blur the message meant for them, making it hard to read.

現在，當一個朋友使用自己的鏡片時，他幾乎看不到給其他朋友的信息。他們看不到足夠多的信息來閱讀其他信息，但幹擾可能足以模糊為他們準備的信息，使其難以閱讀。

The multiple access technology used by 3G networks is called Code Division Multiple Access, or CDMA. It was invented by Qualcomm founder Irwin Jacobs along with many other notable electrical engineers. The technology is based on the concept of spread spectrum, an idea that can be traced back to the early 20th century. Jacobs』 1991 paper showed that CDMA could increase cellular capacity several times over systems at the time.

3G網絡使用的多址技術被稱為碼分多址（CDMA）。它由高通公司創始人歐文·雅各布斯（Irwin Jacobs）和許多其他著名的電氣工程師共同發明。這項技術基於擴頻的概念，這個概念可以追溯到20世紀初。雅各布斯1991年的論文表明，CDMA可以將當時的系統的蜂窩容量提高數倍。

CDMA allows all cell users to transmit and receive their signals at all times and over all frequencies. So if 100 users want to initiate a call or use a cellular service at about the same time, their 100 signals will overlap each other across the entire cellular spectrum for the entire time they are communicating.

CDMA允許所有蜂窩用戶在所有時間和頻率上發送和接收信號。因此，如果100個用戶想要在大約相同的時間發起呼叫或使用蜂窩服務，那麼他們的100個信號將在整個蜂窩頻譜中在他們通信的整個時間內相互重疊。

Overlapping signals create interference. CDMA solves the problem of interference by allowing each user to obtain a unique signature: a code sequence that can be used to retrieve each user’s signal. The symbol corresponds to the color in our paper analogy. If there are too many users on the system at the same time, the codes may overlap. This leads to interference, which gets worse as the number of users increases.

重疊信號會產生幹擾。CDMA通過允許每個用戶獲得唯一的特徵碼來解決幹擾問題：一個可用於檢索每個用戶信號的碼序列。這個符號對應於我們紙上的顏色。如果系統上同時有太多用戶，代碼可能會重疊。這會導致幹擾，隨著用戶數量的增加，幹擾會變得更嚴重。

2 Slices of time and spectrum 時間和光譜切片 （時分多址 TDMA、頻分多址FDMA）

Rather than allowing users to share the entire cellular spectrum at all times, other multiple-access technologies segment access by time or frequency. Segmentation over time creates time slots. Each connection can proceed over multiple time slots distributed in time, but each time slot is so short – a matter of milliseconds – that the mobile user is unaware of the interruptions caused by the alternating time slots. The connection seems to be going on. The slicing technology this time is Time Division Multiple Access (TDMA).

其他多址技術不允許用戶隨時共享整個蜂窩頻譜，而是按時間或頻率分段接入。隨著時間的推移，細分會產生時間段。每個連接都可以在時間上分布的多個時隙上進行，但每個時隙都很短（僅為毫秒），以至於移動用戶不知道交替時隙造成的中斷。這種聯繫似乎正在繼續。這次的切片技術是時分多址（TDMA）。

Frequency division can also be performed. Each communication is given its own frequency band within the cellular spectrum, and the communication is continuous for its duration. This frequency slicing technology is Frequency Division Multiple Access (FDMA).

也可以進行分頻。在蜂窩頻譜中，每個通信都有自己的頻帶，並且通信在其持續時間內是連續的。這種頻率切片技術就是頻分多址（FDMA）。

In our paper analogy, FDMA and TDMA are like dividing the paper into 100 bars in either dimension and writing each private message on one strip. For example, FDMA will be horizontal bars, and TDMA will be vertical bars. Using individual strips, all messages are separated.

在我們的紙張類比中，FDMA和TDMA就像是將紙張在任意維度上分成100條，並將每條私人消息寫在一條紙帶上。例如，FDMA將是水平條，TDMA將是垂直條。使用單獨的條帶，所有消息都被分隔開。

4G/LTE and 5G networks use orthogonal frequency division multiple access (OFDMA), a highly efficient combination of FDMA and TDMA. In the paper analogy, OFDMA is like drawing strips along both dimensions, dividing the entire paper into many squares, and assigning a different set of squares to each user according to their data need.

4G/LTE和5G網絡使用正交頻分多址（OFDMA），這是FDMA和TDMA的高效組合。在紙張類比中，OFDMA就像是沿著兩個維度繪製條帶，將整個紙張分割成許多正方形，並根據每個用戶的數據需求為他們分配一組不同的正方形。

3 End Of 3G? 3G時代的終結？

Now you have a basic understanding of the difference between 3G, 4G/LTE and later 5G. You may still reasonably ask why 3G should be turned off. It turns out that due to these differences in access technology, the two networks are built using completely different equipment and algorithms.

現在，您已經基本了解了3G、4G/LTE和更高版本的5G之間的區別。你可能仍然會合理地問為什麼應該關閉3G。事實證明，由於接入技術的這些差異，這兩個網絡是使用完全不同的設備和算法構建的。

3G phones and base stations operate on a broadband system, which means they use the entire cellular spectrum. 4G/LTE and 5G operate on narrowband or multi-carrier systems, which use segments of the spectrum. These two systems require completely different sets of hardware, from the antenna on your cell tower to the components in your phone.

3G手機和基站在寬帶系統上運行，這意味著它們使用整個蜂窩頻譜。4G/LTE和5G在窄帶或多載波系統上運行，這些系統使用頻譜段。這兩個系統需要完全不同的硬體，從手機發射塔上的天線到手機中的組件。

So if your phone is a 3G phone, it can’t connect to a 4G/LTE or 5G tower. For a long time, cellular providers kept their 3G networks going while building a completely separate network with new tower equipment and servicing new phones with 4G/LTE and 5G. Imagine incurring the cost of running two separate networks at the same time for the same purpose. Ultimately, one has to go. And now, with carriers starting to roll out 5G systems in earnest, it’s time for 3G.

因此，如果你的手機是3G手機，它就無法連接到4G/LTE或5G基站。很長一段時間以來，手機運營商一直在維持其3G網絡的運行，同時使用新的塔式設備構建一個完全獨立的網絡，並使用4G/LTE和5G為新手機提供服務。想像一下，為了同樣的目的同時運行兩個獨立的網絡會產生成本。最終，一個人必須離開。現在，隨著運營商開始認真推出5G系統，是時候結束3G了。

ref:

https://www.lengzhishi.net/profile/hunziyue

https://webghost.bid/end-of-3g-electrical-engineer-explains/

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