IN THE PIPELINE:More Antennas May Be Coming To Cellphones
NEW YORK -- Modern cellphones send snapshots, serve up video games and are quickly replacing traditional long-distance phone service. But making sure calls are heard in their entirety is still a challenge because of the irksome disruptions of "dead zones."
Dead zones result from fading or degradation of the wireless signal that occurs when electromagnetic waves bounce off objects or collide and interfere with one another. Such degradation also cuts short wireless data transmissions, and slows or cuts off wireless Internet access.
A few companies, including Qualcomm Inc. (QCOM) and a little startup called Magnolia Broadband , want to change this by embedding extra antennas inside handsets. Known as "antenna diversity," it's a technology that's been around in a more rudimentary form since the early days of wireless - but in the network rather than the handsets.
Antenna diversity in handsets would increase the capacity of a network, while improving the likelihood the signal from one antenna will get through even when the other signal meets interference. In addition to improving the performance of wireless services, it could allow a carrier to cover more subscribers.
With wireless data files becoming much larger due to photos, games, and, eventually, videos, carriers are looking for more ways to make the most of the spectrum they have. Along with phone manufacturers, they are now considering putting more antennas in handsets.
In recent years, research at various institutions, including Virginia Polytechnic Institute and State University, has demonstrated that installing multiple antennas in mobile devices has extra benefits for wireless performance, even when antenna diversity is already in place in the network. The benefits are particularly clear for data-intensive applications. "Wi-Fi," or high-speed wireless networking, devices, such as PCs that have wireless Internet access, already carry antenna diversity.
Combining Signals
Traditionally, antenna diversity involves switching back and forth between antennas, depending on which is receiving the strongest signal. These are the sorts of systems that have long been in wireless networks and are now being installed in Wi-Fi devices.
"You can do even better if you don't just choose the signals but you combine them together through signal processing," said Dr. James Hicks, a research faculty member at Virginia Tech.
More sophisticated antenna diversity systems involve processing signals from both antennas simultaneously and combining them.
"It's equivalent to allowing you to cup your ears so you can hear from a particular direction better," said Jeff Reed, professor of electrical engineering at Virginia Tech.
These have not been widely installed in devices so far, but some companies are in the late stages of integrating them into mobile handsets, among them Qualcomm.
Carriers in the U.S. and abroad are testing Qualcomm's prototype antenna diversity handsets and the company expects them to hit the market next year.
"We have a lot of interest from CDMA carriers because they see this as a very feasible and cost-effective technique to improve the performance of their phones and of their networks," said Qualcomm Chief Technology Officer Dr. Roberto Padovani.
Qualcomm claims antenna diversity in the handset is only practical for carriers that use the CDMA standard: Verizon Wireless, owned by Verizon Communications (VZ) and Vodafone PLC (VOD); and Sprint PCS Group (PCS) in the U.S. Carriers using the GSM standard, such as AT&T Wireless Services Inc. (AWE), Deutsche Telekom AG's T-Mobile, and Cingular Wireless, owned by SBC Communications Inc. (SBC) and BellSouth Corp. (BLS), would have to switch all their customers to the technology for it to have any benefit, Padovani said. Qualcomm has long been a vocal proponent of the CDMA standard.
By the end of 2004 or early in 2005, Padovani expects that Qualcomm's antenna diversity system won't add more than $2 or $3 to the cost of manufacturing handsets, although they may be initially more expensive.
Coverage will improve as more subscribers get the new handsets, said Padovani. When half of a carrier's subscribers have the handsets, its spectrum will be able to accommodate 50% more subscribers; when all or nearly all are upgraded, the network coverage will double. Qualcomm sees data speed improvements of 50% to 150%.
Qualcomm expects adoption to be very gradual, and that it will be many years before the technology is universally adopted by a carrier's customer base so that its coverage doubles.
Padovani thinks that carriers would initially target certain groups of consumers, although he emphasizes that carriers have not informed him of their plans for distributing the technology. Carriers might first roll out the phones to those with the most expensive plans or those in areas where the spectrum is too crowded, or both, he said.
Targeting high-end consumers would reward those who spend the most. Because these also tend to be the subscribers that send the most weighty files - such as photos and data - it would ease some of the greater strains on the network.
Transmitting And Receiving
One further step in technological evolution involves transmitting as well as receiving signals from multiple antennas. By using two antennas tuned at different frequencies in transmission, the electromagnetic waves that form the cellular signal can combine to form a narrower beam less subject to interference. A feedback system from the network tells the device which antenna is emitting the stronger signal.
"This is one of the hottest areas that I've seen right now," said Reed of Virginia Tech. "There's lots of companies that are looking at this."
One of the first to deploy it may be Magnolia, a three-year old New Jersey company with $15 million in funding.
Magnolia expects to be able to offer carriers prototype handsets to test at the end of this year or early in 2004. Magnolia expects its upgraded handsets to be available to consumers in the second half of next year.
Magnolia says its system has the same correlation between portion of subscribers covered and network capacity improvements as Qualcomm's. A carrier could double its subscribers covered by the same spectrum if its entire subscriber base had the upgraded handsets.
But antenna diversity on the transmission end has additional benefits, according to Magnolia Chief Executive Haim Harel.
It extends a handset's battery life to allow 15% more talking time, or an extra hour, before recharging is required. It also dramatically cuts the risk of harmful emissions from the cellphone, said Harel, acknowledging that whether such emissions are indeed harmful is still being debated.
One of the roadblocks to transmitting wireless signals from more than one antenna has been spacing. The antennas need to have a certain minimum distance between them, and as handsets get smaller, fitting the adequately spaced antennas onto a handset has proved problematic.
But Magnolia says it has a proprietary algorithm that resolves that issue.
Qualcomm is still working on antenna diversity for transmission from the handset.
"That will take definitely more work and longer time," said Padovani, who estimates it will take another four or five years for the company's handset transmit diversity to be complete.
Many people think the technology won't be in high demand before then.
"We believe that most consumers won't generate high data rates, but they will receive high data rates," said Carl Panasik, director of advance architecture in wireless research and development at Texas Instruments Inc. (TXN).
Indeed, Texas Instruments sees this as a technology that can wait for three or four years until cellphones are regularly used to transmit real-time video.
"We're envisioning people watching movies on their handsets; we're envisioning people using them as video phones," said Panasik. "Video unfortunately reveals all the flaws in wireless communications and we'd like to circumvent them if we can today. If I set up a video link and I move my lips, I think you'd like to see that my lips move with the voice and that everything lines up. We don't want this to look like a bad science fiction movie."
But Panasik doesn't see this as an issue for consumers in the next year, and expects it will be another three or four years before Texas Instruments deploys antenna diversity in the handset.
"At the data rates that we move voice, we don't really see this to be a benefit," said Panasik.
多天线手机将消除信号“盲区”
现代化的手机可以拍照，可以打电子游戏，目前正以迅雷不及掩耳之势取代传统的长途电话业务。但由于令人头疼的信号“盲区”的存在，因而要确保通话的完全畅通无阻仍是目前所面临的一大挑战。
当电磁波遇到物体，或电磁波之间发生碰撞互相干扰时，无线信号就会发生衰减，从而产生盲区。无线信号的减弱还切断了无线数据的传输，减缓或中断无线上网服务。
包括高通公司(Qualcomm Inc., QCOM)在内的一些公司，以及一家名为Magnolia Broadband的新创小企业，希望能够通过在手机内嵌入更多天线的方式来改变这种状况。虽然这种天线分集(antenna diversity)技术早在无线通讯出现的初期就作为一种基本的技术部署在网络中，但却一直未进入手机应用领域。
在手机中应用天线分集技术可以提高网络容量，同时增加在一只天线传输信号遇到干扰时，另一只天线传输信号通过的可能性。除能够改善无线服务的性能以外，这一技术还可以扩大无线运营商的用户覆盖。
随著无线数据文档的容量因加载图形、游戏以及视频内容而变得日益庞大，无线运营商正寻求能充分利用其频谱资源的更多方式，其中包括考虑与手机厂商合作，在手机中配置更多的天线。
近年来，包括弗吉尼亚理工学院暨州立大学(Virginia Polytechnic Institute and State University)在内的众多机构所进行的研究均证实，即便就是在网络中已应用天线分集技术的情况下，在移动装置中安装多天线系统对于无线性能还有其他的好处。这些好处在数据密集型应用中表现得尤为明显。个人电脑等具备无线互联网接入能力的高速无线联网(Wi-Fi)装置中目前已经应用了天线分集技术。
整合信号
从传统上来讲，天线分集技术会根据天线接收信号强弱的不同，在天线之间进行切换。这种系统在无线网络中早已有之，而目前正进一步用在Wi-Fi装置中。
弗吉尼亚理工学院研究员詹姆士?希克斯(James Hicks)博士说，如果不仅仅是简单地选择信号，而是通过处理对信号进行整合，其效果会更好。
更先进的天线分集系统能够同时处理并整合来自两只天线的信号。
弗吉尼亚理工学院电子工程教授杰夫?里德(Jeff Reed)说，这和把手放在耳边，以便更清楚地听到某一方向声音的原理一样。
这种技术目前尚未在装置中得到广泛应用，但高通等一些公司在手机中应用这种技术的研发工作目前已处于后期阶段。
美国以及海外的运营商目前正在对高通公司采用天线分集技术的手机样机进行测试。高通公司预计，这种手机将在明年上市。
高通公司首席技术长罗伯托?帕多瓦尼(Roberto Padovani)博士说，CDMA运营商对此很感兴趣，他们认为在提高手机和网络性能方面，这种技术具有切实可行和经济高效的优点。
高通断言，在手机中应用天线分集技术只适用于那些使用CDMA标准的运营商，如：Verizon Communications (VZ)和沃达丰空中通讯公司(Vodafone PLC, VOD)共同持有的Verizon Wireless，以及美国运营商斯普林特PCS公司(Sprint PCS Group, PCS)。帕多瓦尼认为，使用GSM标准的运营商，如：AT&T Wireless Services Inc. (AWE)、德国电信(Deutsche Telekom AG)旗下的T-Mobile、西南贝尔公司(SBC Communications Inc., SBC)和南贝尔公司(BellSouth Corp., BLS)共同所有的Cingular Wireless等公司，将不得不把客户应用移植到这一技术平台上，以提供更先进的服务。
高通公司长期以来一直积极倡导CDMA标准。
尽管高通公司天线分集手机的最初制造成本可能会高一些，但帕多瓦尼预计，到2004年底或2005年初，为此增加的制造成本不会超过2至3美元。
他说，随著更多的用户使用这种新手机，手机网络的覆盖将会得到改善。当一家运营商有半数用户使用这种手机时，其频谱资源能够支持的用户数将增加50%；而当所有或绝大多数用户的手机都升级时，网络的覆盖率将会翻倍。高通公司估计，数据的传输速度因此将可提高50%-150%。
高通公司预计，这种技术的采用需要一个过程，尚须多年时间才能实现在用户中获得普遍应用，并使得覆盖率翻倍。
帕多瓦尼认为，运营商最初可能会锁定一些特定的客户群作为目标，但他强调运营商并未告知他有关这一技术的应用计划。他说，运营商首先可能会向那些资费支出较多，或地处业务繁忙区域，或二者兼而有之的用户，大量推出这种手机。
将目标瞄准高端用户的做法可能是对那些高资费支出用户的一种回报。因为这些用户所发送的信息量（如：照片和数据等）也趋于最多，因此天线分集技术手机对于负担较重的网络将起到一些缓和作用。
传输和接收
技术革命中的下一步工作涉及到复合天线信号的传输和接收。通过使用两只频率不同的天线，产生手机信号的电磁波能够在整合后形成抗干扰能力更强的窄频波束。网络的反馈系统会向装置发出通知，使其选择发射信号更强的天线。
弗吉尼亚理工学院的里德说，这是他目前所见的最为热门的领域之一，许多公司对此极为关注。
最早运用这一技术的公司中，可能包括新泽西州企业Magnolia。这家公司于3年前创立，拥有资本1,500万美元。
Magnolia预计能够在今年底或明年初向运营商提供这种手机样机进行测试，而手机到达用户手中尚须等到明年下半年。
Magnolia称，系统中用户覆盖与网络容量提高之间的相互关系，与高通公司相同。如果运营商的全部用户都将手机升级，则同样频谱所覆盖的用户将会翻倍。
但Magnolia首席执行长安?阿雷尔(Haim Harel)称，在终端中应用天线分集技术还有其他好处。
这种技术将手机一次充电后的待机时间延长了15%。阿雷尔说，这一技术还大大降低了手机有害辐射的风险，但他承认，这种辐射是否确实有害目前还有争议。
通过1个以上的天线传输无线信号的障碍之一，就是天线之间的间距问题。这些天线之间需要有一定的最小间距。随著手机的日益小型化，在手机中装入间距适当的天线一直是一个难题。
但Magnolia称，公司有解决这一问题的独有方法。
高通公司目前仍在致力于天线分集技术应用于手机信号传输的工作。
帕多瓦尼说，这无疑需要付出更多的努力，需要更长的时间。他预计，高通完成这一工作尚须四、五年的时间。
许多人认为，在那之前，对这一技术的需求不会很大。
德州仪器公司(Texas Instruments Inc., TXN)无线研发架构负责人卡尔?帕纳西科(Carl Panasik)认为，多数消费者不会产生高速率的传输要求，但他们将需要高速率的接收服务。
确实，德州仪器认为，在三四年以后，当手机经常性地被用来传输实时视频以后，这一技术就会拥有广阔的需求空间。
帕纳西科说，试想人们在手机上看电影，将手机作为可视电话使用。但不幸的是，视频服务暴露了无线通讯中的所有缺点，如果能够的话，他希望能够避免这些问题。
他说，如果他为手机装上视频链接，并开始讲话，你肯定希望他的口型与声音相匹配。人们不希望这看起来就像是一部拙劣的科幻电影。
但帕纳西科认为，这个问题在明年就不复存在了。他预计，德州仪器在手机中应用天线分集技术还需要三四年的时间。
