Adobe InDesign Tips and Tricks

1. Frames First, Images Second

When you have to place a number of images into your layout, save yourself some effort and first set up the graphic frame with particular specifications (Fit Proportionally, fit content to frame, fit frame to content, etc.). That way you won't have to fidget as much to make the fit.

Drag out the frame to the desired size and proportion. Select Object > Fitting > Frame Fitting Options. Define the Crop Amount or the Reference Point (the point from which your sizes will emanate), and select Fitting > Fit Content Proportionally. Once you define one frame, Option/Alt-drag it to make a duplicate with the same parameters. Now when you Place (Command/Ctrl-D) an image, it will come into the frame with the predefined sizing.

Using the Scissors Tool You can use InDesign's Scissors tool to convert a closed path into an open path and to cut an open path into two separate open paths. First, select it in the Tools panel, and then move the crosshair pointer over the edge of an object. When a circle is displayed in the middle of the crosshairs -- indicating that the pointer is over the edge of the object -- click the mouse button. An anchor point is added where you click. If you select this anchor point with the Direct Selection tool and move it, you'll find another anchor point in the same place. This anchor point is the other endpoint if you cut a closed path. It's an endpoint on a separate path if you cut an open path.

2. Stay Away from System Fonts

When you're preparing InDesign files for print on a Mac, stay away from System fonts. These include the Helvetica, Helvetica Neue, Courier, Symbol, and Zapf Dingbats fonts found in [Your computer] > System > Library > Fonts.

They won't print badly, but the names are the same as PostScript fonts you may also be have. Sometimes the wrong version can be substituted by mistake, causing incorrect spacing or missing characters.

3. New Tabs for Document Windows

If you're not a fan of CS4's tabbed document windows, you can disable them either temporarily or permanently.

Under Window > Arrange, there are commands that let you float one InDesign document outside the tabs or float all InDesign documents outside the tabs. Or simply drag the tab down a bit, and the document becomes a regular floating window.

For the permanent solution, go to Preferences > Interface and turn off the Open Documents as Tabs.

Global Population and the Nitrogen Cycle Part II

As per promise here is Part II

During the early 1960s, affluent nations accounted for over 90 percent of all fertilizer consumption, but by 1980 their share was down below 70 percent. The developed and developing worlds drew level in 1988. At present, developing countries use more than 60 percent of the global output of nitrogen fertilizer. Just how dependent has humanity become on the production of synthetic nitrogen fertilizer? The question is difficult to answer because knowledge remains imprecise about the passage of nitrogen into and out of cultivated fields around the globe. Nevertheless, careful assessment of the various inputs indicates that around 175 million tons of nitrogen flow into the world’s croplands every year, and about half this total becomes incorporated into cultivated plants. Synthetic fertilizers provide about 40 percent of all the nitrogen taken up by these crops. Because they furnish—directly as plants and indirectly as animal foods— about 75 percent of all nitrogen in consumed proteins (the rest comes from fish and from meat and dairy foodstuffs produced by grazing), about one third of the protein in humanity’s diet depends on synthetic nitrogen fertilizer. This revelation is in some ways an overestimate of the importance of the Haber-Bosch process. In Europe and North America nitrogen fertilizer has not been needed to ensure survival or even adequate nutrition. The intense use of synthetic fertilizer in such well-developed regions results from the desire to grow feed for livestock to satisfy the widespread preference for high-protein animal foods. Even if the average amount of protein consumed in these places were nearly halved (for example, by persuading people to eat less meat), North Americans and Europeans would still enjoy adequate nutrition. Yet the statement that one third of the protein nourishing humankind depends on synthetic fertilizer also underestimates the importance of these chemicals. A number of land-scarce countries with high population density depend on synthetic fertilizer for their very existence. As they exhaust new areas to cultivate, and as traditional agricultural practices reach their limits, people in these countries must turn to ever greater applications of nitrogen fertilizer—even if their diets contain comparatively little meat. Every nation producing annually in excess of about 100 kilograms of protein per hectare falls in this category. Examples include China, Egypt, Indonesia, Bangladesh, Pakistan and the Philippines. Too Much of a Good Thing Massive introduction of reactive nitrogen into soils and waters has many deleterious consequences for the environment. Problems range from local health to global changes and, quite literally, extend from deep underground to high in the stratosphere. High nitrate levels can cause life-threatening methemoglobinemia (“blue baby” disease) in infants, and they have also been linked epidemiologically to some cancers. Leaching of highly soluble nitrates, which can seriously contaminate both ground and surface waters in places undergoing heavy fertilization, has been disturbing farming regions for some 30 years. A dangerous accumulation of nitrates is commonly found in water wells in the American Corn Belt and in groundwater in many parts of Western Europe. Concentrations of nitrates that exceed widely accepted legal limits occur not only in the many smaller streams that drain farmed areas but also in such major rivers as the Mississippi and the Rhine. Fertilizer nitrogen that escapes to ponds, lakes or ocean bays often causes eutrophication, the enrichment of waters by a previously scarce nutrient. As a result, algae and cyanobacteria can grow with little restraint; their subsequent decomposition robs other creatures of oxygen and reduces (or eliminates) fish and crustacean species. Eutrophication plagues such nitrogen-laden bodies as New York State’s Long Island Sound and California’s San Francisco Bay, and it has altered large parts of the Baltic Sea. Fertilizer runoff from the fields of Queensland also threatens parts of Australia’s Great Barrier Reef with algal overgrowth. Whereas the problems of eutrophication arise because dissolved nitrates can travel great distances, the persistence of nitrogen-based compounds is also troublesome, because it contributes to the acidity of many arable soils. (Soils are also acidified by sulfur compounds that form during combustion and later settle out of the atmosphere.) Where people do not counteract this tendency by adding lime, excess acidification could lead to increased loss of trace nutrients and to the release of heavy metals from the ground into drinking supplies. Excess fertilizer does not just disturb soil and water. The increasing use of nitrogen fertilizers has also sent more nitrous oxide into the atmosphere. Concentrations of this gas, generated by the action of bacteria on nitrates in the soil, are still relatively low, but the compound takes part in two worrisome processes. Reactions of nitrous oxide with excited oxygen contribute to the destruction of ozone in the stratosphere (where these molecules serve to screen out dangerous ultraviolet light); lower, in the troposphere, nitrous oxide promotes excessive greenhouse warming. The atmospheric lifetime of nitrous oxide is longer than a century, and every one of its molecules absorbs roughly 200 times more outgoing radiation than does a single carbon dioxide molecule. Yet another unwelcome atmospheric change is exacerbated by the nitric oxide released from microbes that act on fertilizer nitrogen. This compound (which is produced in even greater quantities by combustion) reacts in the presence of sunlight with other pollutants to produce photochemical smog. And whereas the deposition of nitrogen compounds from the atmosphere can have beneficial fertilizing effects on some grasslands or forests, higher doses may overload sensitive ecosystems. When people began to take advantage of synthetic nitrogen fertilizers, they could not foresee any of these insults to the environment. Even now, these disturbances receive surprisingly little attention, especially in comparison to the buildup of carbon dioxide in the atmosphere. Yet the massive introduction of reactive nitrogen, like the release of car- Emissions of carbon dioxide, and the accompanying threat of global warming, can be reduced through a combination of economic and technical solutions. Indeed, a transition away from the use of fossil fuels must eventually happen, even without the motivation to avoid global climate change, because these finite resources will inevitably grow scarcer and more expensive. Still, there are no means available to grow crops—and human bodies—without nitrogen, and there are no waiting substitutes to replace the Haber-Bosch synthesis. Genetic engineers may ultimately succeed in creating symbiotic Rhizobium bacteria that can supply nitrogen to cereals or in endowing these grains directly with nitrogen-fixing capability. These solutions would be ideal, but neither appears imminent. Without them, human reliance on nitrogen fertilizer must further increase in order to feed the additional billions of people yet to be born before the global population finally levels off. An early stabilization of population and the universal adoption of largely vegetarian diets could curtail nitrogen needs. But neither development is particularly likely. The best hope for reducing the growth in nitrogen use is in finding more efficient ways to fertilize crops. Impressive results are possible when farmers monitor the amount of usable nitrogen in the soil so as to optimize the timing of applications. But several worldwide trends may negate any gains in efficiency brought about in this way. In particular, meat output has been rising rapidly in Latin America and Asia, and this growth will demand yet more nitrogen fertilizer, as it takes three to four units of feed protein to produce one unit of meat protein. Understanding these realities allows a clearer appraisal of prospects for organic farming. Crop rotations, legume cultivation, soil conservation (which keeps more nitrogen in the soil) and the recycling of organic wastes are all desirable techniques to employ. Yet these measures will not obviate the need for more fertilizer nitrogen in land-short, populous nations. If all farmers attempted to return to purely organic farming, they would quickly find that traditional practices could not feed today’s population. There is simply not enough recyclable nitrogen to produce food for six billion people. When the Swedish Academy of Sciences awarded a Nobel Prize for Chemistry to Fritz Haber in 1919, it noted that he created “an exceedingly important means of improving the standards of agriculture and the well-being of mankind.” Even such an effusive description now seems insufficient. Currently at least two billion people are alive because the proteins in their bodies are built with nitrogen that came— via plant and animal foods—from a factory using his process. Barring some surprising advances in bioengineering, virtually all the protein needed for the growth of another two billion people to be born during the next two generations will come from the same source—the Haber-Bosch synthesis of ammonia. In just one lifetime, humanity has indeed developed a profound chemical dependence.

waiting for your comments

Global Population and the Nitrogen Cycle

Part I 

During the 20th century, humanity has almost quadrupled its numbers. Although many factors have fostered this unprecedented expansion, its continuation during the past generation would not have been at all possible without a widespread—yet generally unappreciated— activity: the synthesis of ammonia. The ready availability of ammonia, and other nitrogen-rich fertilizers derived from it, has effectively done away with what for ages had been a fundamental restriction on food production. The world’s population now has enough to eat (on the average) because of numerous advances in modern agricultural practices. But human society has one key chemical industry to thank for that abundance— the producers of nitrogen fertilizer. Why is nitrogen so important? Compared with carbon, hydrogen and oxygen, nitrogen is only a minor constituent of living matter. But whereas the three major elements can move readily from their huge natural reservoirs through the food and water people consume to become a part of their tissues, nitrogen remains largely locked in the atmosphere. Only a puny fraction of this resource exists in a form that can be absorbed by growing plants, animals and, ultimately, human beings. Yet nitrogen is of decisive importance. This element is needed for DNA and RNA, the molecules that store and transfer genetic information. It is also required to make proteins, those indispensable messengers, receptors, catalysts and structural components of all plant and animal cells. Humans, like other higher animals, cannot synthesize these molecules using the nitrogen found in the air and have to acquire nitrogen compounds from food. There is no substitute for this intake, because a minimum quantity (consumed as animal or plant protein) is needed for proper nutrition. Yet getting nitrogen from the atmosphere to crops is not an easy matter. The relative scarcity of usable nitrogen can be blamed on that element’s peculiar chemistry. Paired nitrogen atoms make up 78 percent of the atmosphere, but they are too stable to transform easily into a reactive form that plants can take up. Lightning can cleave these strongly bonded molecules; however, most natural nitrogen “fixation” (the splitting of paired nitrogen molecules and subsequent incorporation of the element into the chemically reactive compound ammonia) is done by certain bacteria. The most important nitrogen fixing bacteria are of the genus Rhizobium, symbionts that create nodules on the roots of leguminous plants, such as beans or acacia trees. To a lesser extent, cyanobacteria (living either freely or in association with certain plants) also fix nitrogen.

 

A Long-standing Problem

Because withdrawals caused by the growth of crops and various natural losses continually remove fixed nitrogen from the soil, that element is regularly in short supply. Traditional farmers (those in pre-industrial societies) typically replaced the nitrogen lost or taken up in their harvests by enriching their fields with crop residues or with animal and human wastes. But these materials contain low concentrations of nitrogen, and so farmers had to apply massive amounts to provide a sufficient quantity. Traditional farmers also raised peas, beans, lentils and other pulses along with cereals and some additional crops. The nitrogen-fixing bacteria living in the roots of these plants helped to enrich the fields with nitrogen. In some cases, farmers grew legumes (or, in Asia, Azolla ferns, which harbor nitrogen-fixing cyanobacteria) strictly for the fertilization provided. They then plowed these crops into the soil as so-called green manures without harvesting food from them at all. Organic farming of this kind during the early part of the 20th century was most intense in the lowlands of Java, across the Nile Delta, in northwestern Europe (particularly on Dutch farms) and in many regions of Japan and China. The combination of recycling human and animal wastes along with planting green manures can, in principle, provide annually up to around 200 kilograms of nitrogen per hectare of arable land. The resulting 200 to 250 kilograms of plant protein that can be produced in this way sets the theoretical limit on population density: a hectare of farmland in places with good soil, adequate moisture and a mild climate that allows continuous cultivation throughout the year should be able to support as many as 15 people. In practice, however, the population densities for nations dependent on organic farming were invariably much lower. China’s average was between five and six people per hectare of arable area during the early part of this century. During the last decades of purely organic farming in Japan (which occurred about the same time), the population density there was slightly higher than in China, but the Japanese reliance on fish protein from the sea complicates the comparison between these two nations. A population density of about five people per hectare was also typical for fertile farming regions in northwestern Europe during the 19th century, when those farmers still relied entirely on traditional methods. The practical limit of about five people per hectare of farmland arose for many reasons, including environmental stresses (caused above all by severe weather and pests) and the need to raise crops that  were not used for food—those that provided medicines or fibers, for example. The essential difficulty came from the closed nitrogen cycle. Traditional farming faced a fundamental problem that was especially acute in land scarce countries with no uncultivated areas available for grazing or for the expansion of agriculture. In such places, the only way for farmers to break the constraints of the local nitrogen cycle and increase harvests was by planting more green manures. That strategy preempted the cultivation of a food crop. Rotation of staple cereals with leguminous food grains was thus a more fitting choice. Yet even this practice, so common in traditional farming, had its limits. Legumes have lower yields, they are often difficult to digest, and they cannot be made easily into bread or noodles. Consequently, few crops grown using the age-old methods ever had an adequate supply of nitrogen.

 

A Fertile Place for Science

As their knowledge of chemistry expanded, 19th-century scientists began to understand the critical role of nitrogen in food production and the scarcity of its usable forms. They learned that the other two key nutrients—potassium and phosphorus—were limiting agricultural yields much less frequently and that any shortages of these two elements were also much easier to rectify. It was a straightforward matter to mine potash deposits for potassium fertilizer, and phosphorus enrichment required only that acid be added to phosphate rich rocks to convert them into more soluble compounds that would be taken up when the roots absorbed water. No comparably simple procedures were available for nitrogen, and by the late 1890s there were feelings of urgency and unease among the agronomists and chemists who were aware that increasingly intensive farming faced a looming nitrogen crisis. As a result, technologists of the era made several attempts to break through the nitrogen barrier. The use of soluble inorganic nitrates (from rock deposits found in Chilean deserts) and organic guano (from the excrement left by birds on Peru’s rainless Chincha Islands) provided a temporary reprieve for some farmers. Recovery of ammonium sulfate from ovens used to transform coal to metallurgical coke also made a short-lived contribution to agricultural nitrogen supplies. This cyan amide process— whereby coke reacts with lime and pure nitrogen to produce a compound that contains calcium, carbon and nitrogen— was commercialized in Germany in 1898, but its energy requirements were too high to be practical. Producing nitrogen oxides by blowing the mixture of the two elements through an electric spark demanded extraordinary energy as well. Only Norway, with its cheap hydroelectricity, started making nitrogen fertilizer with this process in 1903, but total output remained small. The real breakthrough came with the invention of ammonia synthesis. Carl Bosch began the development of this process in 1899 at BASF, Germany’s leading chemical concern. But it was Fritz Haber, from the technical university in Karlsruhe, Germany, who devised a workable scheme to synthesize ammonia from nitrogen and hydrogen. He combined these gases at a pressure of 200 atmospheres and a temperature of 500 degrees Celsius in the presence of solid osmium and uranium catalysts. Haber’s approach worked well, but converting this bench reaction to an engineering reality was an immense undertaking. Bosch eventually solved the greatest design problem: the deterioration of the interior of the steel reaction chamber at high temperatures and pressures. His work led directly to the first commercial ammonia factory in Oppau, Germany, in 1913. Its design capacity was soon doubled to 60,000 tons a year—enough to make Germany self-sufficient in the nitrogen compounds it used for the production of explosives during World War I. Commercialization of the Haber- Bosch synthesis process was slowed by the economic difficulties that prevailed between wars, and global ammonia production remained below five million tons until the late 1940s. During the 1950s, the use of nitrogen fertilizer gradually rose to 10 million tons; then technical innovations introduced during the 1960s cut the use of electricity in the synthesis by more than 90 percent and led to larger, more economical facilities for the production of ammonia. The subsequent exponential growth in demand increased global production of this compound eightfold by the late 1980s. This surge was accompanied by a relatively rapid shift in nitrogen use between high- and low-income countries.

to be continue..................................

General Info: What is GPRS?

As per promisse here is the next topic from me.......!

GPRS, General Packet Radio Service, allows network operators to offer a packet-oriented data communications service using the current GSM infrastructure. GPRS is an addition to GSM, not a replacement. Network operators will continue to offer circuit switched services alongside the new packet switched service.

The GPRS standardization is currently ongoing within ETSI (European Telephony Standardization Institute) and phase 1 of the standard was ready in the spring of 1998. More services will be introduced in the 2nd phase of standardization. GPRS will offer 2 types of services - Point-to-Point and Point-to-Multipoint. Point-to-Point concentrates on a traditional data communications idea; packets are transferred between two distinct points in the network. The applications for this service are the usual suspects e-mail, web browsing, ftp etc. The Point-to-Point service is defined in phase 1 of the GPRS standardization. Point-to-Multipoint is used when a single user wants to broadcast data to several users simultaneously. Example applications are weather reports, stock market information, and sports results. The Point-to-Multipoint service will be defined in phase 2 of the GPRS standardization. When two different, interconnected hosts wish to communicate they address each other using IP addresses. So, for example, when host Y wishes to send packets to host Z then Z is addressed using its IP address. A GPRS network should appear to other networks as just another IP sub-network where mobiles are addressed using IP addresses. So, when host Y wants to send packets to host X on the GPRS sub-network, Y is oblivious to the fact that X is a GPRS mobile. Packets sent to X are addressed using X's IP address. GPRS also has the ability to connect to other networks. Phase 1 of the standardization process specifies connections to IP and X.25 networks. Other network standards may be added in phase 2.

 

GPRS builds upon the existing GSM infrastructure to provide a packet data service. The parts of the system shown in blue here are those that are part of the traditional GSM system. Those parts in green are the parts of GSM that currently exist but require changes for GPRS. For the BSS it is envisaged that the BTSs will require only a software upgrade. BSCs will probably require both new software and hardware. Those parts shown in yellow are completely new for GPRS these are the GPRS Support Nodes and the internal backbone. The Gateway GPRS Support Node acts as an interface and a router to external networks. The GGSN contains routing information for GPRS mobiles, which is used to tunnel packets through the IP based internal backbone to the correct Serving GPRS Support Node. The GGSN also collects charging information connected to the use of the external data networks and can act as a packet filter for incoming traffic. The Serving GPRS Support Node is responsible for authentication of GPRS mobiles, registration of mobiles in the network, mobility management, and collecting information for charging for the use of the air interface. The internal backbone is an IP based network used to carry packets between different GSNs. Tunneling is used between SGSNs and GGSNs, so the internal backbone does not need any information about domains outside the GPRS network. Signaling from a GSN to a MSC, HLR or EIR is done using SS7. GPRS introduces the concept of a routing area. This is much the same as a Location Area in GSM, except that it will generally contain fewer cells. Because routing areas are smaller than Location Areas, less radio resources are used when a paging message is broadcast. GPRS and GSM use the same physical interface for the radio link, which is based on TDMA with 8 time slots per frame. Each frame is approximately 4.6ms in length. A normal circuit switched telephone call uses the same slot in consecutive frames. Here you can see two speech calls in timeslots 0 and 6, and a fax call in timeslot 2. All are circuit switched and occupy the same slot in every frame. These slots are occupied until the call is cleared. Channel allocation in GPRS is slightly different. A GPRS user is allocated a block, which consists of four timeslots in consecutive frames. Here you can see GPRS user 1 who uses TDMA slots x to x+3, a block of 4 timeslots in consecutive frames. After those slots are used, the same timeslot is allocated to GPRS user 2 who then has access to four slots in frames x+4 to x+7. GPRS user 3 has requested and been allocated two GPRS channels, meaning that double the bandwidth is available to that user. Even so, the channel access is still limited to four timeslots in consecutive frames. 

GPRS subscribers need extra information stored in the Home Location Register. The most important new parameters are shown here. The PDP Type holds the packet data protocol that is currently being used, which can be either IP or X.25. The PDP address contains the address of the mobile which can either be static of dynamic. In the case of dynamic addresses, the address is allocated to the mobile when it first activates a context. The GGSN address is the address of the Gateway GSN that the mobile is currently using. It is possible for operators to have more than one GGSN in the network. Finally there is a quality of service parameter. Exactly how this parameter functions is still subject to a great deal of discussion. The key to a users context is the International Mobile Subscriber Identity. It should also be noted that each user can have several different contexts activated simultaneously, thus allowing the same mobile to operate in different modes if required. For example, one mobile may wish to use IP one day and X.25 the next. After a mobile has attached to the network the context can be chosen with the activated PDP context message. There are three different classes of GPRS mobiles. Class A mobile can handle circuit switched and packet switched data simultaneously. This means a user can receive and transmit data whilst receiving circuit switched telephone calls. Class B mobiles can also connect to both GSM and GPRS and listen for pages from both systems simultaneously. Should the user be operating in packet switched mode, a page for a circuit switched call can still be received. The user then has the choice to switch from one mode to another or ignore the page and return a busy signal. Class C mobiles can only connect to one system at a time. If the user wishes to accept circuit switched calls then they must first remove their connection to the GPRS system and reconnect to GSM. As long as they are operating in packet switched mode no pages for circuit switched calls can be received. One of the most important things to note here is that the application communicates via standard IP, which is carried through the GPRS network and out through the gateway GPRS looks like a normal IP sub-network to users both inside and outside the network. Also notice that packets travelling between the GGSN and the SGSN use the GPRS tunneling protocol so the internal backbone network does not have to deal with IP addresses outside the GPRS network. This GTP is run over UDP and IP. Between the SGSN and the MS a combination of SubNetwork Dependent Convergence Protocol and Logical Link Control is used. SNDCP compresses data to minimize the load on the radio channel. The LLC provides a safe logical link by encrypting packets. The same LLC link is used as long as a mobile is under a single SGSN. When the mobile moves to a routing area that lies under a different SGSN the LLC link is removed and a new link is established with the new Serving GSN X.25 services are provided by running X.25 on top of TCP/IP in the internal backbone. A user wishing to send data does not need to perform any call set-up procedures, remember it's a packet switched network. The data is simply sent to the BTS, which forwards it to the SGSN. The SGSN encapsulates the data and sends it to the GGSN via the internal backbone. Recall that data sent between SGSNs and GGSNs uses tunneling over the internal backbone The GGSN receives the users data packets and forwards it to the external network. The external network then routes it to the destination address. When data is sent from an external user to a GPRS user it arrives at the GGSN via the external network. The GGSN examines the IP address in the incoming packet and uses that to find the address of the Serving GSN. The packet is then tunneled over the internal backbone to the correct SGSN. At this point two things can happen. If the mobile is in a ready state, then the SGSN knows exactly which cell to send the packet to. The packet is simply forwarded to the correct BSC, BTS and finally the GPRS user. If the mobile is in the standby state the SGSN does not know which cell the mobile is in only the routing area is known. In this case a paging message is sent out in the routing area. The mobile responds to the paging message which allows the SGSN to narrow down the MS's location to a single cell. The packet can then be forwarded to the correct BSC, BTS, and finally the user. 

Mobility management in GPRS depends on the current state of the MS. Firstly we'll look at the case when the MS is in the ready state. In the ready state the SGSN knows which cell the MS is in. The mobile knows when it moves from cell A to B and notifies the SGSN of the change. The same process happens when the MS moves from cell B to C as both are under the same SGSN. When the MS moves from cell C to D it also changes SGSN. The mobile marks the change in cells and sends a routing area update to the new SGSN. This routing area update contains the identity of the old routing area, which allows the new SGSN to identify the old SGSN. The new SGSN sends a message to the old SGSN informing it that the MS has changed routing area and is now reachable at the new SGSN address. The old SGSN starts a timer and will forward all packets for the MS to the new SGSN until the timer expires. This prevents any packets from being lost in the handover process. Next the new SGSN informs the GGSN that the MS is now under a new SGSN so new packets can be tunneled to the correct place. The HLR is also informed of the new Serving GSN. For a mobile in the standby state the process is similar. The difference here is that when the MS moves from one cell to another within the same routing area then no updates need to be sent a mobile in the standby state is tracked only on the routing area level. So, the MS is free to move from cell A to B without updating the SGSN as cells A and B are in the same routing area. When the MS moves from cell B to C, which are in different routing areas, then a routing area update is sent to the SGSN. Charging in GPRS is based on the amount of radio resources used and traffic to external networks. The amount of traffic sent inside the GPRS network is tracked by the SGSN. The amount of traffic to and from external networks is tracked by the GGSN. This allows the network operator to charge subscribers for the total network usage.