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Feb. 1, 2001

Wireless vs. Hardwired Networking in Schools

By Jeffrey A. Lupinacci

Many school districts become concerned with networking costs, especially during renovations or new construction. Technology coordinators and network planners are often trying to find ways to reduce costs while providing increased network services. Facility planners and construction managers just want to reduce costs. How can these two opposing goals work together? The correct answer differs in each situation. All politics aside, the district needs to meet its goals of keeping the students up to date with current technology while spending the taxpayer's money responsibly. A look at wireless and hardwired technologies will show that each has its place in the educational environment.

Wireless

Current standards (IEEE 802.11b) support an 11 Mbps DSSS (Direct Sequence Spread Spectrum) Wireless Ethernet LAN (Local Area Network) transmitting at 2.4 Ghz. That sounds very official, but the way it affects the network is to allow an authorized wireless workstation (such as a laptop) a secure shared network connection.

Design documentation states that an area of coverage per antenna is approximately 300 feet indoors and 1,000 feet outdoors at a data rate of 1 Mbps, or 100 feet indoors and 400 feet outdoors at a data rate of 11 Mbps. Actual distances are substantially less.

Wireless LANs require some cabling to be installed for connection of the antennas to the closet-based LAN hub electronics. Approximately one antenna is needed for every eight to ten user connections, which results in a cost reduction of about 87.5% compared with hardwiring the connections.

The benefit of a wireless connection is that it allows the user to move freely around a room or rooms. He is not tethered to the wall in a specific location. Such an environment allows for an increase or decrease in the quantity of workstation connections (within a limited number) without any cable installation work, hardware patching, or advanced notice.

Wireless connections are perfect for those situations where the physical layout of an existing space will not allow a cable to be run--for example, a receptionist in the middle of a marble entrance way. Another good application of the technology is for temporary connections used during class registration or graduation ceremonies. These examples apply the technology with a limited number of users rather than an entire classroom of students.

One problem with a wireless LAN is that the type of network has been touted as a panacea, incorrectly boasting high cost savings for school districts. This causes architects and other non-technical people to try to eliminate required equipment such as cabling and LAN switches to seek these savings. Telecommunications closets are still needed within 100 meters of the wireless access points.

Wireless LANs are a shared technology. The 11 Mbps rate is subject to data packet collisions, as is any CSMA-CD (Carrier Sensing Multiple Access with Collision Detection) protocol. A busy shared network has a utilization rate of 15% for each collision domain. That means that the most busy networks are carrying only 1.65 Mbps shared between approximately eight to ten users, or 200,000 bps per user. During a computer lab course or at the end of a class, when all users hit the file servers or Internet, they will overrun the throughput of the network, possibly slowing the network to a crawl or causing systems to time out and lock up workstations.

Today's wireless systems are designed to provide 11 Mbps at 2.4 Ghz. When the next technology is developed, the current equipment would need to be replaced in order to upgrade.

For general use, a wireless network does not save money. The cost of each NIC (Network Interface Cards) increases from about $67 for a standard card to $180 for a wireless type, almost triple the price. Users who are mobile often use laptop computers rather than desktop computers. Desktop models cost approximately $800, contrasted by the laptop price of $1600, a 100% increase.

Most districts would be unable to convince the parents of students to provide a laptop for their child's use. But assume they were able to provide their own laptops, what would the operating system be? Which word processing software would they buy? It is difficult enough to restrict foreign applications from the network when the machines are owned by the school district; it would be impossible to stop the students from using any application they wanted if the students owned the computers. The problems would increase if the laptop battery was unable to last through the day, and it needed a place to charge or multiple batteries were required.

Hardwired

Most LAN-based protocols are designed to operate over the installed base of cabling or at least the current available cabling systems. Network speeds have increased dramatically over the past ten years from 10 to 1000 Mbps, but the cabling systems have stayed somewhat the same.

The most common standards-based cabling systems in use today are a mix of fiber optic and copper cables. The fiber optics come in single-mode and multi-mode for the backbone subsystem, and the copper cable is Enhanced Category 5 Unshielded Twisted Pair (UTP) to connect the computer to the closet hub. The cabled network operates at speeds well over 100 times faster than the most recent wireless technology. Such a connection is a point-to-point communication path and inherently more secure that a shared wireless connection. The level of interference and radiation is minimized by the cable's design, thus providing a signal of higher integrity and fewer errors.

Network electronics that would be located in a telecommunications closet for the backbone subsystem would be identical for both the hardwired and the wireless network. The horizontal subsystem, or network's edge, differs. Most hardwired LANs use a 10/100 automatic speed-sensing switch for connection to the workstation. This allows a school district to connect to the network with extant 10Mbps NICs and newer 100Mbps NICs without replacing the edge switches. Also capable of operating over an Enhanced Category 5 UTP link is 1000Base-T (Gigabit Ethernet), further protecting your investment for the 'next' technology.

As the hardwired network equipment uses a switch rather than a hub, each workstation is in its own collision domain. That means that there are no other users sharing the cable whose data packet could collide. When a collision occurs on a wireless network, based on how the protocols are designed, each user's packet is lost, a random timer makes them wait for a free time to transmit, and then each must retransmit the information.

The wireless network can provide speeds of only 11 Mbps shared between its users, while hardwired networks operate with a dedicated connection at 100 Mbps switched between two points. Many advancements in LAN technology are pushing the speeds that data travels. More advancement has been technically possible on hardwired LAN as opposed to a wireless LAN. A wireless network, based on transmission speeds, performs like the hardwired networks of ten years ago. The bottom line is the user notices the delays in network response time while using a wireless LAN versus a hardwired LAN.

Hardwired networks can grow without installing additional cables. Each horizontal cable can have a switch connected at the classroom for a cascaded network design. Design standards recommend only one cascade level.

The down side of hardwired networks is that they are difficult to reconfigure. The cabling system should not be moved and manipulated once installed and tested. So when a space changes, new cables are often required.

The skill of technicians installing a cabling plant can effect its performance. If the cable geometry is damaged, it can cause data errors. The technician who performs your installation should be trained on the proper methods. Often, the manufacturer offers this training at no cost.

Case study

As an example, let's look at the costs associated with a typical computer lab with 24 network connections:

Conclusion

Capital expenditure and performance of a network should be analyzed based on cost of all the parts, network operation, and life expectancy. It is preferable to save money today and require no future investment than commit to a technology that will cause you to spend more now as well as in the future. Wireless is an excellent technology for LAN applications--in limited use.

Treat telecommunications in the building like another utility. You may add electrical outlets, but you usually do not remove them. By installing the best quality network cabling you can afford (that is standards-compliant), you can support all network applications available for the foreseeable future without spending more money.

Each school is different and has unique and changing network requirements. The best advice for a district is to establish a strategic plan for technology and work with a reputable designer and contractor to install a system that is flexible and enduring. With funding for such a project very tight, you cannot afford to replace equipment if not absolutely necessary.

Email: Jeff Lupinacci
Jeffrey A. Lupinacci, RCDD/LAN Specialist,
Sr. Telecommunications Designer, Brinjac Engineering, Harrisburg, PA