Cell phone network

FIGURE 18-3 Cell phone networks automatically switch your call from tower to tower as you travel. 

Even the best crisis management plan of FedEx was no match for hurricane Katrina that swept through the gulf coast in 2005. The New Orleans airport was closed for 15 days and FedEx had to return thousands of packages to their senders and stop new shipments to the disaster zones. FedEx shifted its area hub and its employees from New Orleans to Lafayette, Louisiana (135 miles away) in a matter of days. FedEx learned two new things from the Katrina disaster—one is to have temporary housing for displaced employees and second, cell phones cannot be relied on during a disaster since the cell phone networks were down days after Katrina. FedEx has now increased the number of satellite phones that can be deployed. 

In 1947, Bell Labs developed an early cell phone architecture. In the 1960 s, AT T and Motorola competed to develop the first cell phone network in the United States. Inl973, Martin Cooper of Motorola made a phone call to AT T on the DynaTAC, winning the contest. 

Marconi had a dream of a world connected by wireless devices, and as of 2011 that dream is coming true. The IEEE 802 wireless connectivity standards as of 2009 include a personal area network (Bluetooth) that will connect all the devices in a house, car, or office. It has an expanded wireless LAN standard that will support high-speed wireless access of home and office computers into an access point. Both the wireless home network and the wireless LAN can be tied into a high-speed wireless regional network, replacing the current fiber-optic networks. There will be several high-speed cell phone networks that can also tie into the regional wireless system, and when this is added to the current satellite-based wide area networks, the result could be the fully connected wireless world Marconi envisioned. 

Three-dimensional batteries offer a different approach to the portable power field. In this paper we have presented 3-D designs that emphasize power sources with small areal footprints but do not compromise power and energy density. While this approach may not help solve the power needs for cell phones and laptop computers, it will have a significant impact on current and future generations of microdevices. In particular, distributed sensor networks and wireless communication systems are representative areas where 3-D batteries would be welcomed enthusiastically because the power supplies currently in use are many times the size of the device. 

Bluetooth the need for low-cost short-range wireless radio networking among different electronic devices such as mobile PCs, cell phones, and... 

Now let us focus on a specific problem inherent in the scenario described above, namely, maintaining the presence of a user on the network. Current cell phone systems use home location registers (HLRs) and visiting location registers... 

Figure 6.6 I Visible light is just the small portion of the entire electromagnetic spectrum that our eyes can detect. Other regions of the spectrum are used in many technological applications, including remote controls, cell phones, and wireless networks.

Given the supply-chain context of this book, we will consider only the management of independent-demand items—i.e., those items that move between firms in the supply chain. Throughout this book, we focus on issues related to node-to-node relationships in the supply chain, consistent with the framework developed in Chapter 1 that defines a supply chain as a network of nodes. Dependent demand involves "within-node" effects and is outside the scope of this book, but is discussed extensively in books on production/operations planning and control systems (e.g., Vollmann et al., 2005 or Chapman, 2006, which also contains an excellent discussion on hybrid systems that combine appropriate elements of MRP and kanban control). Note, however, that the classification of an item as an independent-demand item or a dependent-demand item is not an absolute characterization. Rather, it only makes sense in context. For example, to the company that assembles the cell phones, the keypad is clearly a dependent-demand item, provided that its only demand is derived from the production schedule for cell phones (i.e., not from sales of keypads as stand-alone items). To the firm that produces the keypads and sells them to various cell phone manufacturers, however, the keypad is an... 

Computer languages are necessary for a wide variety of everyday applications, ranging from cell phones, microwaves, and security systems to banking, online purchases, Web sites, auction sites (such as eBay), social-networking sites (such as Facebook), and Internet search engines (such as Google). 

The field of hber optics focuses on the transmission of signals made of hght through hbers made of glass, plastic, or other transparent materials. The field includes the technology used to create optic h-bers as well as modern applications such as telephone networks, computer networks, and cable television. Fiber optics are used in almost every part of daily life in technologies such as fax machines, cell phones, television, computers, and the Internet. 

The wireless network consists of the wireless (radio) channels connecting the cell phone to the base station. Once a cell phone signal reaches the base station, it travels through copper or fiber to the central office, where it enters the public switched telephone network, or the Internet. The frequencies used for this transmission are extremely valuable, and electronic auctions conducted by the Federal Communications Commission bring in millions of dollars to the U.S. Treasury. 

---