填空题

Beijing 2008: The First 4G Wireless Olympic Games
About half a million years ago, Peking man lived in Zhoukoudian, in the southwestern suburbs of what is now Beijing. If you have been to Beijing more recently, or are at all familiar with modern China, then you know this ancient city is going to host the most modern, high-tech Olympic Games ever in 2008. With technology available today, and a vision for what Beijing could be in 2008, there is an opportunity for the hosts to make the city’s telecommunications infrastructure--in the words of the Olympic motto — "swifter, higher, stronger". The Path to 4G
Beijing has the good fortune of looking at previous generations of wireless networks and avoiding the same mistakes as it prepares for 2008. First Generation (1G) wireless telecommunications — the brick-like analog phones that are now collector’s items—introduced the cellular architecture that is still being offered by most wireless companies today. Second Generation (2G) wireless supported more users within a cell by using digital technology, which allowed many callers to use the same multiplexed channel. But 2G was still primarily meant for voice communications, not data, except some very low data-rate features, like Short Messaging Service (SMS). So-called 2.5G allowed carriers to increase data rates with a software upgrade at the base transceivers Stations (BTS), as long as consumers purchased new phones too. Third Generation (3G) wireless offers the promise of greater bandwidth, basically bigger data pipes to users, which will allow them to send and receive more information.
All of these architectures, however, are still cellular. Cellular architecture is sometimes referred to as a "star architecture’, because users within that cell access a common, centralized base station. The advantage is that given enough time and money, carriers can build nationwide networks, which most of the big carriers have done. Some of the disadvantages include a singular point of failure, no lead balancing, and spectral inefficiencies. The single biggest disadvantage to cellular networks going forward is that as data rates increase, output power will have to increase—or the size of the cells win have to decrease—to support those higher data rates. Since significant increases in output power scare both consumers and regulators, it is far more likely that we will see significantly smaller cells. This will further reduce the return on investment in already fragile 3G business plans.
Fourth Generation (4G) wireless was originally conceived by the Defense Advanced Research projects Agency (DARPA), the same organization that developed the wired Internet. It is not surprising, then, that DARPA chose the same distributed architecture for the wireless Internet that had proven so successful in the wired Internet. Although experts and policymakers have yet to agree on all the aspects of 4G wireless, two characteristics have emerged as all but certain components of 4G:end-to-end Internet Protocol (IP) ,and peer-to-peer(点对点)networking. An all IP network makes sense because consumers will want to use the same data applications they are used to in wired networks. Peer-to-peer networks, where every device is both a transceiver (收发机) and a router (路由器) for other devices in the network, eliminates the weakness of cellular architectures, because the elimination of a single node does not disable the network. The final definition of "4G" will have to include something as simple as this: if a consumer can do it at home or in the office while wired to the Internet, that consumer must be able to do it wirelessly in a fully mobile environment.
Let’s define "4G" as "wireless collaborated peer-to-peer networking". 4G technology is significant because users joining the network add mobile routers to the network infrastructure. Because users carry much of the network with them, network capacity and coverage is dynamically shifted to accommodate changing user patterns. As people congregate and create pockets of high demand, they also create additional routes for each other, thus enabling additional access to network capacity. Users will automatically hop away from congested routes to less congested routes. This permits the network to dynamically and automatically self-balance capacity, and increase network utilization.
What could 4G mean for Beijing and its Olympics
There is a Statistic (without any known attribution) that estimates that the first phone call made by a majority of Chinese alive today was with a cell phone. This would mean that most Chinese skipped a whole generation of telephony (copper twisted pair) and jumped into the world of wireless telephony. So too might the Chinese skip a generation of wireless and deploy a 4G network before 2008. Following are a few applications that could further enhance the Olympic experience, both for the visitors during the Games, and for the residents of Beijing long afterwards.
Security
Beijing has already deployed cameras throughout the city and sends those images back to a central command center. This is generally done using fiber, which limits where the cameras can be hung, i.e., no fiber, no camera. 4G networks allow Beijing to deploy cameras and backhaul(回传) them wirelessly. And instead of having to backhaul every camera, cities can backhaul every third or fifth or tenth camera, using the other cameras as router/repeater.
Traffic Control
Beijing is a challenging city for drivers, with or without an Olympics going on. The growing middle class, and their new-found ability to purchase automobiles, is increasing the number of passenger vehicles on the road at a staggering annual rate of 30%. 4G networks can connect traffic control boxes to intelligent transportation management systems wirelessly, This would create a traffic grid that could change light cycle times on demand, e.g. , keeping some lights green longer temporarily to improve traffic flow. It also could make vehicle-based on-demand "all green" routes for emergency vehicles responding to traffic accidents, reducing the likelihood that those vehicles will themselves be involved in an accident route.
Hot Spots
Beijing could deploy information kiosks(亭)around the city to allow visitors to the Olympics to get real- time information on results, venue updates, and traffic conditions. They could, be backhauled to the Internet via existing cable or DSL. But they could also be home to 802.11 access points, providing free information to any- one with an 802.11 card. And with 4G’s peer-to-peer capabilities, the city could deploy access points even where there is no fiber, by having those "remote" access points hop through backhauled access points. Mobile Hot Spots
To exploit the real power of 4G, Beijing could create mobile hot spots. This would allow users in the sub- ways, trains, and buses to connect to the Internet via standard 802.11 cards talking to standard 802.11 access points. But since those access points obviously cannot be wired to the network, they are connected via 4G wireless networks.
Conclusion
Heating an Olympic Games is, well, an Olympian task. Modern China is more than up to the challenge and it is safe to predict that Beijing 2008 will be one of the most impressive Games of all times. But one other way to measure the success of the Games is the impact it has on the host city after the torch is extinguished. By deploying a 4G mobile broadband network for the Games, Beijing will ensure that its residents will enjoy profound and lasting benefits.
With the help of 4G networks, traffic light cycle period can be adjusted according to ______.