最近三十年来，蜂窝演进与WiFi的物理层比较。(A physical layer comparison of cellular evolution with WiFi over the last three decades.)

The cellular story started in the early 90s when the Global System for Mobile Communications (GSM) became the standard for wireless communication. Before GSM, there were a handful of different analogue communication technologies in use across the world, but they were regional and limited to a select set of countries. In the 1980s, Europe got its countries and industries together to develop a standard for mobile communications. The infrastructure required has been in development for several years before the first GSM call was made in 1991. From there, the technology quickly took off and by end of the 90s, there were hundreds of millions using GSM.

蜂窝的故事始于90年代初，当时全球移动通信系统(GSM)成为无线通信的标准。 在GSM之前，世界上使用了几种不同的模拟通信技术，但是它们是区域性的，并且仅限于部分国家/地区。 在1980年代，欧洲将其国家和行业联合起来，制定了移动通信标准。 在1991年进行第一次GSM呼叫之前，所需的基础设施已经开发了好几年。从那时起，该技术Swift兴起，到90年代末，已有数亿人使用GSM。

When I grew up in the 80s in India, communication between people happened mostly through handwritten letters, and telegrams were to quickly inform people of an emergency. Towards the end of 80s, I saw telegrams replaced by “wired” telephones with “subscriber trunk dialing”, where people call the telephone exchange and ask the operator to make the connection to the number they want to speak to. The telephones were expensive and were still used only for emergencies. We had one telephone per street, and usually someone would come running to our house to inform us that we have a call. By late 90s, most of the middle class households had a telephone.

当我80年代在印度长大时，人与人之间的交流主要是通过手写信件进行的，而电报则可以Swift通知人们发生紧急情况。 到80年代末，我看到电报被“用户中继线拨号”所取代的“有线”电话所取代，人们在其中打电话给电话交换机，并要求接线员与他们要通话的号码建立连接。 这些电话很昂贵，仍然仅用于紧急情况。 我们每条街道只有一部电话，通常会有人跑到我们家通知我们有电话。 到90年代后期，大多数中产阶级家庭已经有了电话。

Technology usually takes time to percolate down to everyone. But wireless communication has reached people faster than, say, computers. Commercial computers were available in mid 1970s, but the first computer I saw was in 1995, when my school purchased one. That is two full decades and it took even more time to become a common sight in households. Compare that to everyone I knew in India having a mobile phone by mid 2000, in just a little over a decade of commercial mobile communications, half the time as what it took for computers. The reason for this partly is opening up of Indian economy in 1991, but it is not hard to believe that communication between people matters to the populace far more than personal computers. But enough of me reminiscing and opining. You came here for a comparison between cellular and wifi evolution, so let us dive right into that.

技术通常需要时间才能渗透到每个人。 但是无线通讯的普及速度比计算机快。 商用计算机在1970年代中期问世，但我见到的第一台计算机是1995年，当时我的学校购买了一台计算机。 这是整整二十年的时间，花了更多时间才成为家庭的普遍现象。 与我所认识的每个印度人相比，到2000年中期，在商业移动通信的短短十年时间里，手机的使用时间是计算机的一半。 造成这种情况的部分原因是1991年印度经济的开放，但人们不难相信人与人之间的交流对个人的影响远大于对个人计算机的影响。 但是，我足以让我想起和接受。 您来这里是为了比较蜂窝和wifi的发展，因此让我们直接了解一下。

Here is the trailer!

这是预告片！

起点：GSM和802.11b (The Beginning: GSM and 802.11b)

GSM was the first commercially successful digital mobile communication technology, where we generate “data bits” and pass it through a channel encoder to generate “coded bits” which are then mapped to “symbols” digitally before converted to analog using a digital to analog (DAC) converter, then up converted into radio frequency (900 or 1800 MHz) and transmitted over air. GSM is a single carrier system with a bandwidth of 270 KHz using time division duplex (TDD) to utilize the same frequency channel for downlink (transmission from base station to user equipment) and uplink (transmission from user equipment to base station). It opted for convolutional encoding as the forward error correction scheme and Gaussian minimum shift keying (GMSK) for digital modulation.

GSM是第一种在商业上成功的数字移动通信技术，在该技术中，我们生成“数据位”，并将其通过通道编码器以生成“编码位”，然后将其“数字”映射为“符号”，然后使用数模转换为“模拟”( DAC)转换器，然后向上转换为射频(900或1800 MHz)并通过空中传输。 GSM是使用时分双工(TDD)带宽为270 KHz的单载波系统，以利用相同的频率信道进行下行链路(从基站到用户设备的传输)和上行链路(从用户设备到基站的传输)。 它选择使用卷积编码作为前向纠错方案，并选择高斯最小频移键控(GMSK)进行数字调制。

GMSK can be viewed as a form of “frequency shift keying”, where bit 0 is mapped to one frequency and bit 1 is mapped to another frequency. But GMSK can also be implemented using a quadrature modulator (with both sine and cosine modulators for converting baseband signal to RF) because of its connection to offset-QPSK, where the I and Q are overlapped so that at any given time, there is phase transition only in I or Q.

GMSK可以看作是“频移键控”的一种形式，其中位0映射到一个频率，位1映射到另一频率。 但是GMSK也可以使用正交调制器(同时使用正弦和余弦调制器将基带信号转换为RF)来实现，因为它与offset-QPSK相连，其中I和Q重叠，因此在任何给定时间都存在相位仅在I或Q中转换。

This being a single carrier system, the receiver required a time domain equalizer to compensate for the multipath channel impairments. Advanced receivers used maximum likelihood sequence estimation (MLSE) that is based on the Viterbi algorithm.

这是一个单载波系统，接收器需要一个时域均衡器来补偿多径信道的损害。 高级接收器使用基于维特比算法的最大似然序列估计(MLSE)。

The initial usage was for voice only with a circuit switched network — which means a connection between two devices needs to be established before information is exchanged between them and this connection is held until the call is disconnected. This requires blocking a part of the switch capacity for each connection. By late 90s, GPRS (General Packet Radio Service) was added for data transfer and kick started evolution of core network to be “packet” based. I must stop short of discussing the “evolved packet core” and restrict myself to my area of expertise, so let us get back to the physical layer.

最初的用法仅用于电路交换网络中的语音-这意味着在两个设备之间交换信息之前，需要在两个设备之间建立连接，并且保持该连接，直到呼叫断开为止。 这需要为每个连接阻塞一部分交换机容量。 在90年代后期，增加了GPRS(通用分组无线服务)以进行数据传输，并开始了基于“分组”的核心网络的发展。 我必须停止讨论“演进的分组核心”，而将自己限制在我的专业领域，因此让我们回到物理层。

Late 90s, GSM is well established across the world for mobile voice communication, but the hunger of data is growing. Internet is becoming popular and access to that enormous collection of information was starting to change the world. No wonder people wanted wireless access to it so as to not be tied to the DSL (digital subscriber line) modem with a wired connection. Laptops were getting into the market around this time too, offering mobility compared to desktop computers, and if computers can be carried around, why not internet? The time was ripe for wireless access to the internet, and enter IEEE 802.11 standard — Wireless Local Area Network.

上世纪90年代后期，GSM在全球范围内已经建立了完善的移动语音通信技术，但是数据的需求却在不断增长。 互联网正变得越来越流行，对大量信息的访问开始改变世界。 难怪人们想要无线访问它，以便不通过有线连接绑定到DSL(数字用户线)调制解调器。 笔记本电脑也在这段时间也进入了市场，与台式机相比提供了移动性，如果可以随身携带计算机，为什么不上网呢？ 无线访问Internet的时机已经成熟，并进入IEEE 802.11标准-无线局域网。

The first of the 802.11 set of standards, now grouped under 802.11b, jumped the gun on GSM and adopted spread spectrum as the technology for communication, allowing it to use a massive 22 MHz bandwidth to transmit data rates up to 2 Mbps. Compare this to the measly 230 Kbps offered by GPRS, and it is a 10 fold increase!

802.11b标准的第一个标准，现在归类为802.11b，在GSM上大放异彩，并采用了扩频作为通信技术，从而使其能够使用22 MHz的巨大带宽来传输高达2 Mbps的数据速率。 与此相比，GPRS仅提供了230 Kbps，而且增加了10倍！

Like GSM, 802.11b is single carrier modulation and the receiver uses time domain equalization for symbol recovery. By 1999, 802.11b amendment introduced some enhancements that increased the data rate to 11 Mbps!

像GSM一样，802.11b是单载波调制，接收器使用时域均衡进行符号恢复。 到1999年，802.11b修正案引入了一些增强功能，将数据速率提高到11 Mbps！

构建：WCDMA和802.11a / g (The Buildup: WCDMA and 802.11a/g)

It takes two to Tango, and now that WLAN has led the way by adopting spread spectrum, cellular must follow! Andrew J. Viterbi, the inventor of the Viterbi algorithm and co-founder of Qualcomm, made significant contributions in bringing Code Division Multiple Access (CDMA), which was based on direct sequence spread spectrum, to reality in cellular. There were some competing implementations during this process — CDMA 2000 was adopted by the USA as an answer to GSM in Europe, but was quickly replaced by Wideband CDMA (WCDMA) in early 2000s. WCDMA is popularly known as 3G, and the core-network too evolved at this point to support packet based architectures for handling the IP (internet protocol) traffic.

探戈需要两个人，现在WLAN已通过采用扩频引领了潮流，蜂窝必须紧随其后！ 维特比算法的发明者，高通公司的共同创始人安德鲁·维特比(Andrew J.Viterbi)为将基于直接序列扩频的码分多址(CDMA)引入蜂窝技术做出了重大贡献。 在此过程中，存在一些竞争性的实现方式-CDMA 2000被美国采纳为欧洲GSM的解决方案，但在2000年代初Swift被宽带CDMA(WCDMA)取代。 WCDMA通常被称为3G，并且核心网络在这一点上也得到了发展，以支持用于处理IP(互联网协议)流量的基于数据包的体系结构。

WCDMA, the physical layer technology adopted by UMTS (Universal Mobile Telecommunications System) included support for Frequency Division Duplex (FDD) access, which means a pair of channels, one for downlink and one for uplink, can simultaneously transmit and receive signals on air. Until now, both GSM and WLAN has been opting for TDD, but introduction of FDD in cellular removed the inconvenience of devices having to wait for reception while delaying the data to be transmitted. This is not the only one-upmanship, but WCDMA also introduced the near-capacity achieving Turbo codes as the error correction scheme — one of the best inventions channel coding research had on offer at the time. Turbo codes are based on parallel concatenated convolutional codes, and soft-output Viterbi algorithm is used as component decoder in iterative decoding to get very close to Shannon capacity limit. The game is afoot!

WCDMA是UMTS(通用移动电信系统)采用的物理层技术，包括对频分双工(FDD)接入的支持，这意味着一对信道(一个用于下行链路，一个用于上行链路)可以在空中同时发送和接收信号。 到目前为止，GSM和WLAN都一直在选择TDD，但是在蜂窝中引入FDD消除了设备在等待接收数据同时延迟传输数据的麻烦。 这不仅是唯一的一项，而且WCDMA还引入了接近容量的实现Turbo码作为纠错方案—信道编码研究当时提供的最佳发明之一。 Turbo码基于并行级联卷积码，在迭代解码中使用软输出维特比算法作为分量解码器，以非常接近香农容量极限。 游戏正在进行中！

But oh my, WLAN changed the game again! Introduced multi-carrier with OFDM (Orthogonal Frequency Division Multiplexing) in the early 2000 and supported peak data rates of 54 Mbps! It specified operation in both the 2.4 GHz (802.11g) and 5 GHz (802.11a) unlicensed bands.

但是，我的WLAN再次改变了比赛！ 在2000年初推出了具有OFDM(正交频分复用)功能的多载波，并支持54 Mbps的峰值数据速率！ 它规定了在2.4 GHz(802.11g)和5 GHz(802.11a)非许可频段中的操作。

WCDMA, which was based on 5 MHz bandwidth, introduced HSPA (High Speed Packet Access) with higher order modulation (up to 64 QAM), multiple antennas (up to 4x4 MIMO) to get to peak data rates of 42.2 Mbps. Still a bit shy of the 54 Mbps that WLAN can provide, but the difference is mobility. Cellular is designed for outdoor connectivity, focusing on maintaining connection over very long distances and at high speeds, where as WLAN is meant for indoor connectivity and low mobility environments.

基于5 MHz带宽的WCDMA引入了具有更高阶调制(高达64 QAM)和多个天线(高达4x4 MIMO)的HSPA(高速分组接入)，以达到42.2 Mbps的峰值数据速率。 WLAN仍然可以提供54 Mbps的传输速度，但还是有所差异。 蜂窝网络专为室外连接而设计，专注于在很长距离和高速度下保持连接，而WLAN则用于室内连接和低移动性环境。

Not satisfied, cellular tried playing the multi-carrier game with WCDMA, introducing carrier aggregation with first DC-HSPA (dual carrier) and later MC-HSPA (multi carrier), where two or more carriers/channels can be aggregated into one data pipe, offering a way to increase bandwidth and thus the data rate.

不满意，蜂窝网络尝试使用WCDMA玩多载波游戏，引入第一个DC-HSPA(双载波)和后来的MC-HSPA(多载波)的载波聚合，其中两个或更多载波/信道可以聚合到一个数据管道中，从而提供一种增加带宽，从而增加数据速率的方法。

3GPP (the 3rd Generation Partnership Project), a global consortium of industries and the standardizing body for cellular technology, by now realized that OFDM is instead an elegant way of doing multi-carrier than the complex carrier aggregation on WCDMA. It is a Tango after all, and where when one partner leads, the other must follow!

3GPP(第三代合作伙伴计划)是一个全球性的产业联盟，是蜂窝技术的标准化机构，目前已经意识到，与WCDMA上的复杂载波聚合相比，OFDM是一种替代多载波的优雅方式。 毕竟，这是一个探戈，当一个伙伴领导时，另一个必须跟随！

But hold on though, the carrier aggregation is not going away and will make a surprise entry again.

但是，尽管如此，载波聚合并没有消失，并且将再次令人吃惊。

演进：LTE和802.11n / ac / ax (The Evolution: LTE and 802.11n/ac/ax)

Move over WCDMA, the next gen is here! Enter LTE (Long Term Evolution) in 2008, adopting OFDM as the physical layer multiple access technology. Now cellular can go toe to toe with WLAN.

超越WCDMA，下一代就在这里！ 在2008年进入LTE(长期演进)，采用OFDM作为物理层多址技术。 现在，蜂窝网络可以与WLAN相互竞争了。

But wait, cellular has led with MIMO and Turbo codes. It is time for WLAN to catch up with a follow! WLAN introduced 802.11n in 2009, with up to 4x4 MIMO and the capacity achieving Low-Density-Parity-Check (LDPC) codes for error correction. WLAN also increased the bandwidth to be not just 20 MHz as it was for 802.11a/g, but also 40 MHz, resulting in a whopping peak data rate of 600 Mbps. Beat that cellular!

但是，等等，蜂窝技术以MIMO和Turbo码为首。 现在是WLAN赶上追随者的时候了！ WLAN在2009年推出了802.11n，具有高达4x4 MIMO的能力，并且能够实现低密度奇偶校验(LDPC)码以进行纠错。 WLAN不仅将带宽提高到了802.11a / g的20 MHz，而且还提高了40 MHz，从而使峰值数据速率达到了600 Mbps。 击败手机！

In turn, or in return, LTE is going to make not just one, but a whole sequence of moves!

反过来，或者作为回报，LTE不仅会采取行动，而且还会采取一系列行动！

The first LTE release with bandwidth options 1.4, 3, 5, 10, 15 and 20 MHz and 2x2 MIMO provided a peak data rate of 150 Mbps in downlink and 50 Mbps uplink. Then came the support for 4x4 MIMO before upping the game with LTE-Advanced (LTE-A).

具有带宽选项1.4、3、5、10、15和20 MHz以及2x2 MIMO的首个LTE版本在下行链路和上行链路上提供了150 Mbps的峰值数据速率。 然后是对4x4 MIMO的支持，然后才使用LTE-Advanced(LTE-A)升级游戏。

Carrier aggregation made a comeback in LTE-A as the option to increase bandwidth and up to 5 component carriers can be aggregated. This coupled with support for up to 8 layer spatial multiplexing (8x8 MIMO) allows for theoretical peak data rates of 3 Gbps in downlink.

由于增加带宽的选择，载波聚合在LTE-A中卷土重来，最多可以聚合5个分量载波。 加上对多达8层空间多路复用(8x8 MIMO)的支持，可以在下行链路中实现3 Gbps的理论峰值数据速率。

Between 2011 to 2017, in different releases, LTE-A also introduced an array of options encompassing an umbrella of use cases:

在2011年至2017年之间，LTE-A在不同版本中还引入了一系列选项，涵盖了一系列用例：

1. Inter Cell Interference Coordination (ICIC) to mitigate interference from neighboring base stations. The base stations talk to each other and decide the schedule for Almost Blank Subframes (ABS) so that when one base station is transmitting, the interfering base station transmits ABS to minimize the interference. Further enhancements also provide an option for the base station to not use the subcarriers that neighboring base station uses for CRS (Cell-specific Reference Signal) to transmit the control and data channel. Advanced user equipment can also estimate the channel from neighboring base station’s CRS to do interference cancellation for those subcarriers.小区间干扰协调(ICIC)，以减轻来自相邻基站的干扰。 基站相互通信，并确定“几乎空白子帧”(ABS)的调度，以便在一个基站发送信号时，干扰基站发送ABS以使干扰最小化。 进一步的增强还为基站提供了不使用相邻基站用于CRS(特定于小区的参考信号)来发送控制和数据信道的子载波的选项。 高级用户设备还可以估计来自相邻基站CRS的信道，以对那些子载波进行干扰消除。
2. Coordinated Multi Point (CoMP) transmission to improve throughput at cell edge, either via dynamic point selection (either one of the two base stations can transmit to the UE depending on channel quality measurement from UE) or via joint transmission using appropriate beamforming weights.协调多点(CoMP)传输可通过动态点选择(两个基站中的一个可以根据来自UE的信道质量测量结果发送到UE)来提高小区边缘的吞吐量，也可以通过使用适当的波束成形权重的联合传输来实现。
3. Discontinuous Reception (DRX) to schedule the user equipment (UE) to go to sleep and save power. Transmission to the UE are sent only during the period UE is awake.非连续接收(DRX)，以调度用户设备(UE)进入睡眠状态并节省电量。 仅在UE处于唤醒状态期间才发送到UE的传输。
4. Narrow Band Internet of Things (NB-IoT) provides for the IoT use cases where the device requires very low throughput. This is achieved by using a bandwidth of one resource block unit that is 180 KHz, either from the guard band or from within the bandwidth.窄带物联网(NB-IoT)提供了设备需要非常低吞吐量的IoT用例。 这可以通过使用一个180 KHz的资源块单元的带宽(从保护频带或从带宽之内)来实现。
5. Device to Device (D2D) communications allows for communication between two UE devices by introducing “sidelink” channels with its own primary and secondary synchronization signals. This is easy to do in WLAN where there is no difference between downlink and uplink transmissions, but LTE uses OFDMA in downlink and SC-FDMA (single carrier frequency division multiple access, which is DFT precoded OFDM) in uplink. Since UE receivers are designed to only receive downlink transmission, entirely new channels are introduced for D2D support.设备到设备(D2D)通信通过引入带有其自己的主要和辅助同步信号的“侧链路”信道，允许两个UE设备之间进行通信。 在下行链路和上行链路传输之间没有区别的WLAN中，这很容易做到，但是LTE在下行链路中使用OFDMA，在上行链路中使用SC-FDMA(单载波频分多址，即DFT预编码OFDM)。 由于UE接收机被设计为仅接收下行链路传输，因此引入了全新的信道来支持D2D。
6. V2X (vehicle to everything) to support communication during high speed mobility between autonomous cars.V2X(车辆应有尽有)可支持自动驾驶汽车之间高速移动时的通信。

Not all of these options are implemented, deployed and commercially available, but the support is present in the standard.

并非所有这些选项都已实现，部署并在商业上可用，但是标准中提供了支持。

To catch up during all these moves, WLAN introduced 802.11ac with support for up to 8x8 MIMO and bandwidth options of 20, 40, 80 and 160 MHz, operating in both 2.4 GHz and 5 GHz bands. With 160 MHz bandwidth and 8 layer spatial multiplexing, peak data rates can theoretically reach 3.4 Gbps. The physical layer catches up with LTE-A, but the WLAN MAC is still encumbered by CSMA-CA (Carrier Sense Multiple Access and Collision Avoidance) resulting in all the scheduling benefits in OFDMA is being missed out by WLAN. Realizing that later in the game, IEEE standardized 802.11ax in 2019, bringing the goodness of OFDMA to AP (access point) scheduling, and introducing TWT (Target Wake Time) to provide a similar power saving option like DRX. The subcarrier spacing was also reduced (from 312.5 KHz to 78.125 KHz) in 802.11ax to allow for better resource allocation across users, and this enabled peak data rates up to 9.6 Gbps when using 8x8 MIMO and 160 MHz bandwidth. This is no longer orders of magnitude higher than cellular as it once was, but still a reasonable 3x larger.

为了赶上所有这些步伐，WLAN引入了802.11ac，它支持高达8x8 MIMO和20、40、80和160 MHz的带宽选项，并在2.4 GHz和5 GHz频段上运行。 凭借160 MHz带宽和8层空间复用，理论上的峰值数据速率可以达到3.4 Gbps。 物理层赶上了LTE-A，但是WLAN MAC仍然受CSMA-CA(载波侦听多路访问和冲突避免)的困扰，导致OFDM错过了OFDMA中的所有调度优势。 在游戏的后期意识到这一点，IEEE在2019年对802.11ax进行了标准化，将OFDMA的优点带到了AP(接入点)调度中，并引入了TWT(目标唤醒时间)来提供类似DRX的节能选项。 在802.11ax中，子载波间隔也减小了(从312.5 KHz减小到78.125 KHz)，以便更好地在用户之间分配资源，并且在使用8x8 MIMO和160 MHz带宽时，这使峰值数据速率高达9.6 Gbps。 它不再比以前的蜂窝网络高几个数量级，但仍是合理的三倍。

But by the time IEEE standardized 802.11ax, 3GPP had already begun work on the next step in the evolution — the 5G New Radio (5GNR). The dance is reaching a crescendo!

但是，到IEEE标准化802.11ax出现时，3GPP已经开始着手进行演进的下一步工作-5G新无线电(5GNR)。 舞步渐渐高涨！

未来：5GNR和802.11be (The Future: 5GNR and 802.11be)

Cellular continues the lead, but must also copy some of the moves from WLAN to stay in sync. After all, it is still Tango!

蜂窝网络继续领先，但也必须复制WLAN中的某些移动以保持同步。 毕竟，它仍然是探戈！

The new radio (NR) adopts LDPC codes as the error correction scheme, taking a leaf out of the WLAN dance book. But it also leads by adopting brand new state-of-the-art Polar codes as error correction for control channels, finally moving away from convolutional codes completely.

新的无线电(NR)采用LDPC码作为纠错方案，从而使WLAN舞蹈书从中脱颖而出。 但是，它也采用了全新的最新Polar代码作为控制通道的纠错技术，从而最终完全摆脱了卷积代码。

But that is not all, 5GNR also introduces scalable numerology by allowing for several subcarrier spacing options, the 15 KHz used in LTE, and multiples of it: 30, 60 and 120 KHz. This scalability enables NR to be used on any frequency band from sub 1 GHz to 100 GHz. The lower frequencies (sub 6 GHz) will continue to use 15 KHz subcarrier spacing to provide for long range, but higher frequency bands (26 GHz and 39 GHz) can use larger subcarrier spacing to increase the bandwidth up to 400 MHz per carrier, while at the same time shortening the TTI (Time to Transmit Interval) due to smaller OFDM symbol size. NR also ups the game by introducing flexible scheduling of time frequency resources by allowing transmission to start at any symbol instead of the subframe boundaries in LTE.

但这还不是全部，5GNR还通过允许几个子载波间隔选项(LTE中使用的15 KHz以及30、60和120 KHz的倍数)引入了可扩展的数字学。 这种可扩展性使NR可以在低于1 GHz到100 GHz的任何频带上使用。 较低的频率(低于6 GHz)将继续使用15 KHz子载波间隔以提供长距离，但是较高的频带(26 GHz和39 GHz)可以使用较大的子载波间隔将带宽提高到每个载波400 MHz，而同时由于较小的OFDM符号尺寸而缩短了TTI(发送间隔时间)。 NR还通过引入灵活的时频资源调度(通过允许传输从任何符号开始而不是LTE中的子帧边界开始)来提高游戏质量。

But the biggest of all is massive MIMO! WLAN always had the edge in beamforming since the channel feedback in WLAN sends the full precoding matrix computed by the receiver, and this precoding matrix can be used by the other transmitter to realize the maximum beamforming gain. The LTE beamforming gain however was limited by the finite set of precoding matrices from which the receiver must select the best one. With massive MIMO, NR can use hybrid beamforming techniques to form a pencil beam in the UE directions. Beam scanning followed by UE feedback is used to find the direction of the UE. These are still early days of NR, and the technology is still evolving. But there is enormous promise here!

但是最大的是大规模MIMO！ 由于WLAN中的信道反馈发送了接收机计算出的完整预编码矩阵，因此WLAN在波束成形中始终处于优势地位，并且该预编码矩阵可以被其他发射机使用，以实现最大的波束成形增益。 但是，LTE波束成形增益受到一组有限的预编码矩阵的限制，接收机必须从中选择最佳的一组。 通过大规模MIMO，NR可以使用混合波束成形技术在UE方向上形成笔形波束。 在UE反馈之后进行波束扫描以找到UE的方向。 这些仍是NR的早期，技术还在不断发展。 但是这里有巨大的希望！

Similarly, WLAN is continuing to work on the future, christened 802.11be (Extreme High Throughput) and some of the initial directions seems to be taking inspirations from LTE Co-MP (multi-link) and soft combining with HARQ (Hybrid Automatic Repeat Requests). We will have to wait and see what the future holds, but the dance goes on!

同样，WLAN仍在继续发展，被称为802.11be(极高吞吐量)，并且某些初始方向似乎是从LTE Co-MP(多链路)以及与HARQ(混合自动重复请求)的软结合中获得灵感的)。 我们将拭目以待，看看未来会怎样，但舞蹈仍在继续！

获胜者，冠军 (The Winner)

So who is the winner? It is the communications engineers! Delighted with the academic research coming into practice and happy to build the systems required for it. During the two decades of my association with Wireless Communications, there were a few algorithms/techniques that I got excited about, but they never made it to practice: algebraic geometry codes with list decoding, iterative modulation and decoding, interference cancellation to achieve single channel full duplex operation, are some of them. But the technology adoption is speeding up and academic research is no longer that much ahead of the curve. Polar codes invented in 2008 has been adopted in 5GNR and that is research coming to practice within a decade. With this trend speeding up, I can get my hands on the recent advances in Communications theory without being a researcher in academia, but as an engineer building products and seeing the theory practically in action. What can be more awesome than that!

那么谁是赢家？ 是通讯工程师！ 高兴地将学术研究付诸实践，并乐于构建所需的系统。 在我与无线通信协会的二十年间，有一些令我兴奋的算法/技术，但他们从未付诸实践：带列表解码，迭代调制和解码，消除干扰以实现单通道的代数几何代码全双工操作，就是其中一些。 但是，技术的采用正在加速，学术研究不再遥遥领先。 5GNR已采用了2008年发明的Polar码，并且这项研究将在十年之内付诸实践。 随着这种趋势的加快，我可以在没有学术界研究人员的情况下接触通信理论的最新进展，而可以作为工程师来构建产品并在实践中看到该理论。 有什么比这更棒的了！

https://www.linkedin.com/in/prasannasethuraman/

https://www.linkedin.com/in/prasannasethuraman/