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.
譯文：
如何突破4G無線網絡的瓶頸
使用更多的頻譜和先進的天線，蜂窩網絡供應商和運營商計劃在接下來的幾年中推出該技術以提高4G網絡的速度。但是蜂窩技術已經達到無線電信號本身可以攜帶的物理瓶頸，因此研究人員正在尋找其他方式來提高速度和4G網絡的容量，幾乎所有這些技術都將使用名爲LTE的標準。對研究人員來說，未來網絡提速的關鍵是縮短用戶和基站的距離，並且允許他們自動重新配置。
從歷史上看，新一代移動設備需包含兩個基本部分：移動通信標準和頻譜分配，Hakan Djuphammar如是說，他是愛立信無線電設備架構和組合製造商的副總裁。
由於LTE達到了物理可能性的瓶頸，所以現在不太可能從頭開始定另一個標準，Djuphammar如是說，因爲一個新的標準不可能改變物理定律。另一個問題是一個新的技術標準不能真正解決已變得越來越分散的頻譜分配問題，因爲電波現在已如此擁擠。
Djuphammar說，所謂的異質網，或異構網絡的發展，關鍵是移動網絡如何發展。HET網使用的傳統大型基站和更小的單元格混合機制，放置在那裏有很多用戶的領域。其基本思路是與今天的蜂窩基站相同，這個最經常放在家中以增加網絡的空閒部分，同時提高覆蓋並使得訂閱者能更好的連接到它。但在HET網，小型基站將與餘下的網絡結合更多。它要建設的網絡結構要支持2G，3G，4G，並在大多數情況下支持Wi – Fi在設備之間不同形式的跳轉訪問，根據不同網絡的負載和當前應用。
Djuphammar說，這些網絡結構也將動態管理設備採用智能的方式訪問。但這是一個非常具有挑戰性的任務，他說。相同的光譜頻段也將用於不同的移動通信標準。這要看連接到基站的是哪種設備，該基站可以通過改變頻譜的使用量，以最大限度地發揮實時性能。
“今天我們還是靜態的分配頻譜，但在未來這將是完全動態的。例如，如果在一個地區中沒有電話需要使用GSM，那麼整個頻譜都可用於4G。但是當一個GSM手機回到該區域，基站將重新分配其頻譜，“Djuphammar說。
瑞典皇家理工學院已開始研究2020年的網絡會是什麼樣。我們的目標是一千倍的帶寬增長，KTH無線電通信無線系統無線的教授及其中心的負責人Zander如是說。桑德爾是一個密集網絡的支持者，這種網絡的地方基站之間的距離較短，因此每段有更高有效承載能力。“超越LTE的，我認爲最重要的事情是尋找在短距離內又好又便宜的解決方案，並像Wi – Fi一樣易於安裝，但有更高的容量並更好的協調網絡空閒部分，“Zander說。
簡化安裝過程中的一個重要組成部分，是自組織網絡的概念，它允許運營商或用戶將基站連接到網絡，並且它會被自動安裝。 “當前網絡成本的很大一部分是他們必須要精心策劃，”Zander說，4G網絡的短期改善將包括更多的頻譜和多天線的使用。
連續頻譜是一種有限的資源，因此供應商提出載波聚合，允許運營商把在不同頻段的頻譜聚在一起，並像一條數據鏈路一樣來使用。擴容的另一種方法，如今已廣泛使用，就是MIMO天線技術，它使用在基站的多路天線和設備上來提高速度；更多的天線意味着更多的帶寬。多輸入多輸出（MIMO）天線需要看到無線電信號版本的細微差別，天線之間的距離讓它們能夠做到這一點。MIMO的一大挑戰是要滿足用戶設備上的所有需求。桑德爾說，在移動電話上同時適用兩個以上的天線非常困難。由於使用更大的屏幕，許多高端智能手機的尺寸在不斷擴大，這將會有所幫助。筆記本電腦和平板電腦更適合使用多天線，正是因爲它們有着較大的尺寸。