原文：
By Mikael Ricknäs | IDG News Service
Using more spectrum and advanced antennas, cellular network vendors and operators plan to increase 4G mobile speeds as that technology rolls out over the next several years. But cellular technology has hit a fundamental wall in the physics of what the radio signals themselves can carry, so researchers are looking at other ways to increase speed and capacity of 4G networks, nearly all of which will use a standard called LTE. the keys to increasing speeds as researchers look at future networks are to shorten the distance between users and base stations and allowing them to automatically be reconfigured.
Historically, a new mobile generation has included two basic components: a mobile standard and spectrum allocation, says Håkan Djuphamma , vice president of architecture and portfolio at radio equipment maker Ericsson.
Because LTE is at the limit of what is physically possible, it now makes less sense to develop another standard from the ground up, Djuphammar says, as a new standard couldn't change laws of physics. Another issue that a new technology standard can't really address is that the allocation of spectrum has become increasingly fragmented because the airwaves are so crowded.The development of so-called het nets, or heterogeneous networks is key to how mobile networks evolve, says Djuphammar. Het nets use a mixture of traditional large base stations and smaller cells, placed in areas where there are a lot of users. The basic idea is the same as with today's femtocells, which are most often placed in homes to offload the rest of the network, while also improving coverage and providing better capacity for subscribers connected to it. But in a het net, the smaller base stations would be more integrated with the rest of the network.It's about building network structures that would allow devices with 2G, 3G, 4G, and in most cases Wi-Fi to jump among different forms of access depending on the load in the different parts of the network and the application currently used. These network structures would also dynamically manage device access in an intelligent way, says Djuphammar. But doing all that is a pretty challenging task, he says.The same spectrum bands would also be used for different mobile standards. Depending on what kind of devices are connected to a base station, that station could change the amount of spectrum used to maximize performance in real time. "Today we have a static allocation of spectrum, but in the future it will be completely dynamic. For example, if there are no phones in a cell that need to use GSM, the entire spectrum can be used for 4G. But when a GSM phone comes back into the cell, the base station again reconfigures its spectrum allocation," Djuphammar says.Sweden's KTH Royal Institute of Technology has started to examine what networks could look like by 2020. The aim is a thousand-fold capacity increase, says Jens Zander, a professor in Radio Communications at the university and head of its center for wireless systems Wireless@KTH. Zander is a big proponent of denser mobile networks where the distance between base stations is much shorter and thus there's higher effective carrying capacity per segment."Beyond LTE, I think the most important things are finding good and cheap solutions over short distances and having base stations that are as easy to install as Wi-Fi but have much higher capacity and have better coordination with the rest of network," Zander says.An import part of simplifying the installation process is the concept of self-organizing networks, which allow operators or users to connect a base station to the network and it would automatically be installed. "A big part of the cost for current networks is that they have to be carefully planned," Zander says.Short-term improvements to 4G networks will include the use of more spectrum and multiple antennas. Continuous spectrum is a limited resource, so vendors have come up with carrier aggregation, which allows operators to bunch together spectrum in different bands and use them as one data link.Another way to increase capacity, which is already used today, is MIMO antenna technology, which uses multiple antennas in the base station and on the device to increase speeds; more antennas mean more capacity. For MIMO to work, the antennas need to see a slightly different version of the radio signal, which the distance between the antennas allow them to do.The big challenge with MIMO is to fit all the needed antennas on the user device. It is very difficult to fit more than two antennas in a mobile phone, says Zander. The growing size of many high-end smartphones, thanks to the use of larger screens, will help. Laptops and tablets are more amenable to the use of multiple antennas due to their larger sizes.
译文：
如何突破4G无线网络的瓶颈
使用更多的频谱和先进的天线，蜂窝网络供应商和运营商计划在接下来的几年中推出该技术以提高4G网络的速度。但是蜂窝技术已经达到无线电信号本身可以携带的物理瓶颈，因此研究人员正在寻找其他方式来提高速度和4G网络的容量，几乎所有这些技术都将使用名为LTE的标准。对研究人员来说，未来网络提速的关键是缩短用户和基站的距离，并且允许他们自动重新配置。
从历史上看，新一代移动设备需包含两个基本部分：移动通信标准和频谱分配，Hakan Djuphammar如是说，他是爱立信无线电设备架构和组合制造商的副总裁。
由于LTE达到了物理可能性的瓶颈，所以现在不太可能从头开始定另一个标准，Djuphammar如是说，因为一个新的标准不可能改变物理定律。另一个问题是一个新的技术标准不能真正解决已变得越来越分散的频谱分配问题，因为电波现在已如此拥挤。
Djuphammar说，所谓的异质网，或异构网络的发展，关键是移动网络如何发展。HET网使用的传统大型基站和更小的单元格混合机制，放置在那里有很多用户的领域。其基本思路是与今天的蜂窝基站相同，这个最经常放在家中以增加网络的空闲部分，同时提高覆盖并使得订阅者能更好的连接到它。但在HET网，小型基站将与余下的网络结合更多。它要建设的网络结构要支持2G，3G，4G，并在大多数情况下支持Wi – Fi在设备之间不同形式的跳转访问，根据不同网络的负载和当前应用。
Djuphammar说，这些网络结构也将动态管理设备采用智能的方式访问。但这是一个非常具有挑战性的任务，他说。相同的光谱频段也将用于不同的移动通信标准。这要看连接到基站的是哪种设备，该基站可以通过改变频谱的使用量，以最大限度地发挥实时性能。
“今天我们还是静态的分配频谱，但在未来这将是完全动态的。例如，如果在一个地区中没有电话需要使用GSM，那么整个频谱都可用于4G。但是当一个GSM手机回到该区域，基站将重新分配其频谱，“Djuphammar说。
瑞典皇家理工学院已开始研究2020年的网络会是什么样。我们的目标是一千倍的带宽增长，KTH无线电通信无线系统无线的教授及其中心的负责人Zander如是说。桑德尔是一个密集网络的支持者，这种网络的地方基站之间的距离较短，因此每段有更高有效承载能力。“超越LTE的，我认为最重要的事情是寻找在短距离内又好又便宜的解决方案，并像Wi – Fi一样易于安装，但有更高的容量并更好的协调网络空闲部分，“Zander说。
简化安装过程中的一个重要组成部分，是自组织网络的概念，它允许运营商或用户将基站连接到网络，并且它会被自动安装。 “当前网络成本的很大一部分是他们必须要精心策划，”Zander说，4G网络的短期改善将包括更多的频谱和多天线的使用。
连续频谱是一种有限的资源，因此供应商提出载波聚合，允许运营商把在不同频段的频谱聚在一起，并像一条数据链路一样来使用。扩容的另一种方法，如今已广泛使用，就是MIMO天线技术，它使用在基站的多路天线和设备上来提高速度；更多的天线意味着更多的带宽。多输入多输出（MIMO）天线需要看到无线电信号版本的细微差别，天线之间的距离让它们能够做到这一点。MIMO的一大挑战是要满足用户设备上的所有需求。桑德尔说，在移动电话上同时适用两个以上的天线非常困难。由于使用更大的屏幕，许多高端智能手机的尺寸在不断扩大，这将会有所帮助。笔记本电脑和平板电脑更适合使用多天线，正是因为它们有着较大的尺寸。