VoIP Protocols and Wide-Area Networks

With the large scale rollout of wireless Ethernet-based VoIP phones in the enterprise, VoIP technology has reached a level of maturity where residential VoIP cordless phones, wireless PBXs and, eventually, future cellular systems based on 802.11 are no longer just a possibility for VoIP over WLAN technology—they are inevitable.

The larger challenge of VoIP over WLANs will be how to handle handoffs of an active call between 802.11 APs or between an 802.11 AP and a cellular network's cell. VoIP residential cordless phones will be the only application that will not require handoff capabilities initially.

The following diagram illustrates the basic mobility challenge for WLAN implementations:

Figure 12
Figure 12

As the diagram illustrates, the hierarchical nature of IP network topology results in two types of mobility:

  • Micro-Mobility
  • Macro-Mobility
Micro-mobility and macro-mobility are defined as changes of access point association (attachment) while an ongoing VoIP (or data) session is in progress. They define the requirements for handoffs in the larger system. Micro- and macro-mobility differ from WLAN roaming or nomadic operations where a session is simply terminated and restarted in a new 802.11 AP cell. (This is what happens in WLAN hotspots today.)

Micro-mobility is the simplest form of mobility. The subscriber is moving within a single domain, such as an enterprise, a set of hotspots owned by company A or some other sort of limited WLAN configuration. Micro-mobility essentially involves intra-domain handoffs. There is no need for external coordination. Issues of timing, call control and handoff control can be set (or bounded) by network design. The first wave of VoIP over WLAN services will be based on micro-mobility in the enterprise or in the residence.

Macro-mobility involves moving between two domains that fall under the administration of completely distinct organizations. For example, one hotspot could be run by carrier A and a second is administered by carrier B. The two domains must collaborate to complete the handoff and to conduct authentication, authorization and accounting (AAA) activities between the domains. These arrangements are similar to efforts in the cellular industry that have been developed over the last few years.

Given that micro-mobility solutions will be the first developed and deployed, micro-mobility solutions must consider the larger framework that includes macro-mobility capabilities as well as the eventual evolution to full macro-mobility.

There are two principal approaches for supporting mobility in VoIP services. They are:

  • SIP (Session Initiated Protocol)
  • Mobile IP
Mobile IP is a network layer (i.e. layer 3) approach to mobility. While Mobile IP does not directly support VoIP applications, the protocol can be used as a basis for VoIP with additional and potentially proprietary protocols (e.g. Cisco's CCx). The alternate solution is to confront the mobility challenge at the application layer (layer 4/5) by augmenting existing VoIP protocols like SIP or H.323. Currently, the inclusion of SIP in Microsoft Windows® XP has resulted in widespread support and a proliferation of the infrastructure for the simpler SIP protocol over the more rigid H.323 protocol.

The following section gives a brief overview of Mobile IP and SIP for mobility applications and concludes with a discussion of cellular GPRS/WLAN integration for data services. Many in the industry anticipate that cellular data deployments like GPRS/WLAN will be implemented initially and a larger movement to full blown VoIP WLANs will follow later.

Mobile IP Overview

Several elements are needed to implement a WLAN incorporating Mobile IP capabilities for APto- AP handoffs. The following diagram illustrates the elements of a Mobile-IP system:

Figure 13
Figure 13

The elements shown above are defined as follows:

  • Mobile Node: VoIP caller
  • RFA: Regional Foreign Agent
  • AAAF: Authentication, Authorization, Accounting - Foreign Network
  • GFA: Gateway Foreign Agent
  • HA: Home Agent
  • AAAH: Authentication, Authorization, Accounting - Home Network
  • CN: Corresponding Node (the network that a caller node is attached to)
  • Caller Node: Another phone caller

Figure 14
Figure 14

When both caller and the mobile node are in the home network (i.e. when the switching occurs within one's own voice network), the PBX function is present. In this case, the VoIP call is routed through a self-contained enterprise network and no Internet domain resources are required.

Mobile IP is based on the concept that a mobile node has a home address associated with a home network. Each time the mobile node connects to a foreign network, it obtains a temporary address which is known as a Care of Address (CoA). The CoA is valid while the mobile node is attached to the foreign network domain. It is deleted or purged from the foreign network once the mobile node leaves the domain.

In Mobile IP WLANs, there are two mobility agents, Home Agents (HA) and Foreign Agents (FA), that coordinate, update and authorize the connections and associated CoAs for clients from foreign networks. When a call is set up between a Caller Node and the Mobile Node, a binding update message is sent by the Home Agent to the Corresponding Node. The binding message allows VoIP traffic and messages to be directly tunneled between the Caller Node and the Mobile Node. Messages need not be routed to the home network. Clearly, tunneling greatly increases the efficiency of Mobile IP.

Difficulty arises when roaming occurs between two foreign networks while a call is in progress between a Caller Node and a Mobile Node. Consider a Mobile Node that is leaving one foreign network and transitioning to a new foreign network. The first foreign network and associated FA must send binding warning messages to the caller's Home Agent (HA), alerting the HA that packets from the CN are arriving, but the Mobile Node is no longer in the first foreign network. The first foreign network redirects any received packets back to the caller's HA. Simultaneously, the Mobile Node will complete the association with the second foreign network. The HA then will establish the new CoA with the second Foreign Agent / foreign network. The HA then provides a new CoA to the second foreign network, and this allows direct tunneling of messages between the Mobile Node on the second foreign network and the caller node in the corresponding network. While this handoff is taking place, the HA acts as a middle man, maintaining the VoIP connection by forwarding packets from the first foreign network to the second foreign network. This stops once the new CoA and binding for direct tunneling are in place.

A complete description of this process is beyond the scope of this paper. However, it is obvious that when the problem is reduced to a single domain (such as an enterprise WLAN where there are no foreign networks), the solution is much more tractable.

In addition to the overall handoff process, controlling several timing issues is imperative for successful macro-mobility and micro-mobility handoffs. The following are some of the timing elements that must concern WLAN or handset designers:

  • Ts: The period of time needed for a station to associate with an access point (probe and associate)
  • Tf: The period of time needed by a handset to associate with a foreign network (inter-domain update)
  • Th: The period of time to bind to a foreign network and create a new CoA
  • Tmc: The period of time needed to send packets directly between the Mobile Node and a Caller Node
  • Tno: The period of time needed to bind update messages from an old foreign network to a new foreign network
The time required to register and set up a VoIP call for Mobile IP is:

Tmip_init = 2Ts + 2Th + 2Tmc

For macro-mobility (inter-domain) handoffs between two different foreign networks, Mobile IP has the following timing:

Tmip_inter = Tno + 3Th + Thc + Tmc

During a handoff, as the new tunnel connection is established between a Mobile Node and the Caller Node, a series of packets will be disrupted and may arrive out of order, causing them to be discarded. The period of time for this disruption is given by the same formula for both SIP and Mobil IP. It is:

Tblack_out = 2 Ts + 2 Th + 2 Tno

For micro-mobility handoffs in the same domain, such as a handoff from one AP to another in an enterprise WLAN, Mobile IP has the following timing:

Tmip_intra = 2Ts + 2Tf

At this point, issues relating to intra-domain handoffs will be discussed. In the next section, the SIP approach and its associated timing issues will be described.

Issues for Mobile IP Macro-mobility

There are two major issues relating to the implementation of Mobile IP macro-mobility:

  • The probe and association time for 802.11 APs is not included in the time delay budgets in the previous discussion. This will exacerbate handoff delays unless improvements are made.
Lost packets may result in short disruption in voice services.
A more important issue is the fact that Mobile IP is not widely supported. The end-to-end deployment of Mobile IP on the Internet will take significant effort to achieve.

SIP Overview

As an alternative to Mobile IP, SIP supports IP mobility for VoIP WLAN applications by providing handoff capabilities at the application layer.

SIP can make direct use of Dynamic Host Control Protocol (DHCP) when connecting to an 802.11 AP for binding an IP address. A number of proposed systems use DIAMETER as the AAA (authentication, authorization, accounting) protocol. SIP makes use of the concept of a visited registrar (VR) in the foreign network. The SIP VR combines some of the functions of a SIP proxy server, location server and user agent. The SIP proxy server concept allows SIP to handle both firewall functions and network address translations (NAT), which are pervasive in home network topologies. SIP was initially designed to support roaming (i.e. moving into a domain while the connection is disabled and then establishing service) so that a user could be found independently of location and network device. For example, with SIP a call on a handheld phone could be transferred to a computer SIP phone. SIP is being modified to support mobility as well as roaming applications.

Like Mobile IP, macro-mobility in an SIP implementation would be based on the concept of foreign networks and home networks. With SIP, the foreign agent of Mobile IP is replaced by an SIP VR in the foreign network. The Mobile IP home agent (HA) is replaced by an SIP home registrar (HR). The SIP HR is a combination of an SIP proxy server, a location server and a user agent server. The following diagram illustrates an SIP network:

Figure 15
Figure 15

The elements in this type of network are defined as follows:

  • Mobile Node: VoIP caller
  • DHCP: Dynamic Host Control Protocol
  • AAAF: Authentication, Authorization, Accounting - Foreign Network
  • SIP VR: Visited Registrar
  • SIP HR: Home Registrar
  • AAAH: Authentication, Authorization, Accounting - Home Network
  • CN: Corresponding Node (the network that a caller node is attached to)
  • Caller Node: Another phone caller
When VoIP callers are in their home networks or a self-contained enterprise network that has implemented SIP-based micro-mobility, the VR (visited registrar) is removed and replaced by an HR (home registrar). This is shown in the following diagram:

Figure 16
Figure 16

One of the principal differences between Mobile IP and SIP is the use of DHCP by 802.11 APs. DHCP doubles the number of transactions needed to associate with an access point. It also requires that the client perform an ARP (Address Resolution Protocol) to detect duplicate addresses in the sub-net. The advantage of DHCP is that no modification to the local network is needed.

While there are minor differences between Mobile IP and SIP, the handoff procedures are essentially identical. SIP has the advantage of using the existing IP network without modification. However, this comes at the expense of delays that are typically double those of Mobile IP in a macro-mobility environment.

To its advantage, SIP is fully supported today by the Windows environment (i.e. Windows XP), making possible a rapid deployment in the residential/SOHO marketplace.

Just as with Mobile IP, timing issues must be addressed if SIP handoffs are to be supported. For the most part, SIP's timing elements are identical to those for Mobile IP. The only exception is SIP's use of the Address Resolution Protocol (ARP). In the formulas below, Tarp is defined as the period of time needed for an ARP exchange.

The time required to register and set up a VoIP call with SIP is the following:

Tsip_init = 4Ts + Tarp + 2Th + 2Tmc

(addition of 2Ts + Tarp vs. Mobile IP)

For macro-mobility (inter-domain) handoffs between two different foreign networks, SIP has the following timing:

Tsip_inter = 4Ts + Tarp + 2Th + 2Tmc

(For initially establishing service, SIP's timing is identical to Mobile IP, but much greater than Tmip_inter)

The blackout time for SIP and Mobile IP is given by:

Tblack_out = 2 Ts + 2 Th + 2 Tno

For micro-mobility (intra-domain) handoffs such as an enterprise-based AP-to-AP handoff in the same domain, Mobile IP has the following timing:

Tmip_intra = 4Ts + Tarp + 2Tf

(addition of 2Ts + Tarp vs. Mobile IP)

As these formulas indicate, by using the existing IP network without modification, SIP suffers from delays that can be 2x those of Mobile IP.

SIP for Residential and SOHO Use

SIP can be used on an existing netwok without modification.

SIP is designed into Windows XP and will be in Windows CE

SIP suffers from delays that can be 2x those of Mobile IP. In a larger network, these delays quickly become unacceptable.

For cordless phone VoIP applications in the home, the delay in SIP is negligible and its ease-of-integration will greatly facilitate product introduction.

IPv6 and Protocol Improvement

These discussions of Mobile IP and SIP have assumed WLAN deployments on IPv4 networks. Both SIP and Mobile IP would greatly benefit from the pervasive use of IPv6. In both cases this would allow direct addressing of a mobile node client. If Mobile IP and SIP were revised in light of IPv6, the Foreign Agent could be removed entirely and handoff times would improve.

For Mobile IP to succeed, it must be deployed pervasively. As a result, there is interest in the industry in SIP for consumer applications.

Wide Area Network Integration: WLAN and GPRS Inter-working
While the ultimate goal is to provide seamless IP mobility for all applications including voice, in the near term cellular carriers are planning to integrate data operations through a combination of 802.11 for hotspots and cellular telephony technology for wide area data networking.

This section briefly describes the integration of the cellular GPRS (General Packet Radio System) standard with WLAN technology in a seamless data network. This process will take several steps, including:

  1. Common billing and customer care but no inter-working of WLAN and GPRS networks.
  2. A 3GPP-based access control and charging system where all WLAN AAA (authentication, authorization, accounting) will be based on GPRS AAA procedures.
  3. Access to GPRS data services such as WAP are supported on the WLAN system, but there are no handoffs between WLAN and GPRS.
  4. Where jitter and time delay permit, there would be service continuity for the services described in item three above. These services would be provided across the WLAN and GPRS networks. The handoff of IP multimedia may not be supported, but other IP services would be.
  5. Seamless continuity where all services are supported transparently between WLAN and GPRS networks. There is no noticeable difference in the services.
  6. Access to 3GPP switched circuit services is provided and voice services are supported.
There are essentially two schools of thought on how WLANs should interface to the existing GPRS network. These views are:
  • Tightly coupled WLAN network
  • Loosely coupled WLAN network
A tightly coupled network is illustrated in the following diagram. The tightly coupled network makes use of all existing GPRS system resources for networking, AAA, security, provisioning and other functionality. These functions are coupled to the WLAN systems. With minor exceptions, the WLAN user will have immediate access to all GPRS services. This type of system would use a strong GPRS inter-working function (GIF) to interface to the WLAN network, and all traffic would be routed through the Serving GPRS Support Node (SGSN).

Figure 17
Figure 17

A loosely coupled network is illustrated in the following diagram. This loosely coupled scheme would be based on Mobile IP. Only minor modifications to installed WLAN networks would be required. However, cellular operators would need to install AAA servers for billing mediation and to support WLANs as well as to support interoperations between the GPRS network and WLANs. In a loosely coupled system, the Internet is used as the traffic backbone. Because service operators would not have complete control over the network, there is some concern that consistent quality might not be provided.

Figure 18
Figure 18


Category Tight Coupling Loose Coupling
Authentication GPRS authentication and cipher key encryption SIM based authentication/Optional Radius based
Accounting Reuse GPRS accounting External Billing for common accounting
WLAN Cellular Mobility SSGN Call Anchor, mobility by iner-SSGN handovers Home Agent (HA) is the call anchor, mobile IP between access router and GGSN (gateway)
Context Transfer Fine grain info on QoS, flows, etc. limited information between GGSN and WLAN (IETF working on "seamboy")
System / Network Engineering Impact on WLAN traffic to existing GSN bearer and signaling is an issue WLAN and GPRS can be designed spearately
New Development WLAN modification for GPRS for GPRS signaling, possible SGSN modes. CAG for SIM-based authentication, Billing mediator for accounting
Standards A new SSN interface EAP-Sim and EAP-AKA authentication (IETF Ppext working group)
Target Usage Applies to Cellular owned WLAN or affliated WISP Broad Application

Table 13

The deployment of WLAN hotspots has taken on a life of its own. It may not be practical to require conformance to certain standards or to modify existing WLAN equipment with cellular security and signaling. The motivation of carriers is clear. Carriers require control over network quality. They also are concerned that Mobile IP has not been widely deployed and, because of this, seamless interfaces may be delayed. Carriers also are concerned that when QoS capabilities are deployed, they may be haphazard at best. Clearly, all indications from the marketplace would suggest that the deployment of seamless networks of WLAN and cellular technology will happen in the near future. Indeed, certain cellular carriers already have acquired and are supporting WLAN hotspot networks, merging the billing and customer care operations for the two technologies.

Access Time Delay

Regardless of the application, the time delay and jitter of the VoIP system will be a design consideration. As already noted, the two following issues relate to time delay and jitter:

  1. Signaling for call set up, tear down and other call control communications will be delayed. (Worst case delay is the principal concern.)
  2. Jitter in the voice traffic/bearer channel will cause delay.
VoIP signaling and voice traffic are not separate communications channels. VoIP packets exist as virtual communications within a single channel. Only queuing priorities can ensure timely delivery of voice packets when other types of packets are competing for services in an IP network. This situation is complicated when a wireless user is moving and there are AP-to-AP handoffs in the network. Further delays are added into the WLAN as the user must associate with an AP, authorization must take place and the handoff must be completed.

The ITU has set recommendations for the maximum round trip delay in a voice system and the perceived quality of the voice channel. This recommendation is defined in ITU G.113 and is provided in the following table:

G.113 Delay Specification
0 to 150 msec acceptable to most applications
150 to 400 msec acceptable for international connections
> 400 msec acceptable for public network operation
Table 11

Under normal operations, the roundtrip delay should be less than 150 msec. The following diagram illustrates the possible delays in the communication path for an enterprise network with one layer of routing.

Figure 10
Figure 10
Because delay in the PSTN backbone network is beyond the control of mobile device manufacturers, the following table illustrates a residual delay budget for the backbone network (Tbackbone) using short duration G.711 and G.726 VoIP packet structures. The data for this table is taken from measurements that were performed on VoIP software implementations and from worst case delays in an extensive wireless enterprise network.

Round Trip Delay Source Delay Symbol G.711 (5msec) G.726 (10msec)
Encode / Decode Tenc_dec 5.5 5.5
Assemble / Disassemble Tasm 10 20
Jitter Buffer (1) Tbuf 10 20
WLAN Access Delay Taccess 10 20
Access Point Routing Tap_route 10 10
Enterprise Routing Trouting 5 5
Backbone Delay (residual) Tbackbone 99.5 69.5
Total 150 150

(1) Tbuf can be set as large as Tbackbone
Tabel 12

These figures indicate that the G.726 residual backbone delay will be less than 70 msec, but there is some concern in the industry that in countries with large geographic areas, such as the U.S., Canada and others, the backbone network delay may exceed 70 msec.

For a VoIP cordless phone, the equivalent diagram of the communication path would remove the enterprise router and feature a minimum of 10 msec of additional delay margin (the maximum delay for the POTS PSTN network). The residential delay path is shown in the following diagram:

Figure 11
Figure 11
Any effects communication delay could have on voice quality for a fixed implementation of VoIP over WLAN is readily ameliorated, but larger issues arise when a user is handed off from one AP to another.

In a cellular phone system, a great deal of effort is expended on the handoff operation. The handoff is typically completed in 35 msec with 50 msec being worst case. WLAN systems do not have the interconnect processing capabilities or higher-order switching intelligence that is built into cellular networks. In a WLAN, the following capabilities are relevant to the network's ability to hand off active phone calls:

  1. The WLAN must know when a link has been lost. (This can be a simple rule, such as losing more than N/M packets.)
  2. AP probe and associate.
    1. Currently, tests by the University of Maryland show that an AP probe takes place in 250 to 400 msec.
    2. Significant effort to improve both AP-to-AP handoffs and authentication are being addressed by the IEEE 802.11 committee's 802.11i (security) and 802.11e (QoS) task groups.
  3. Authentication, security and routing updates.
    1. Delays of more than three seconds have been caused by centralized authentication servers.
Clearly, dramatic improvements are needed in AP probe, authentication and routing update operations. WLANs have delays for handoffs nearly 10 times greater than handoffs in cellular systems.

During the handoff between 802.11 APs, there will be short but noticeable loss of voice packets. On the positive side, VPN and call agent servers have timeouts on the order of tens of seconds. While some VoIP packets may be lost in a WLAN, connection should be maintained.

Several proposals for solving the hand-off delay problem have been proposed. These include:

  1. Nearest neighbor or sub-net authorization proxy (authorization across a sub-net).
  2. Highest QoS priority to an AP's probing services.
  3. Shadow registration in enterprise WLANs. That is, a subscriber will be pre-registered and authorized within a sub-net.

FDA reports more cases of salmonella illnesses


WASHINGTON - The government on Saturday increased the number of people reported being sickened in a record salmonella outbreak in which tomatoes are the leading suspect although investigators are testing other types of fresh produce.

There have been 943 reported cases nationwide, with at least 130 hospitalizations since mid-April after the first salmonella illnesses appeared, the Food and Drug Administration said Saturday. That compares with a total of 922 people about two days ago and 869 reported earlier in the past week.

The FDA also said it had begun looking at jalapeno peppers as a possible cause of the outbreak, as well as ingredients used to make salsa such as cilantro and Serrano peppers. Tomatoes continue to be investigated as well, spokeswoman Stephanie Kwisnek said.

On Tuesday, the government said it would test numerous other kinds of fresh produce commonly served with fresh tomatoes while insisting that tomatoes remained the leading culprit.

Investigators with the Centers for Disease Control and Prevention have interviewed people sickened in June to find out what they ate and to compare their diets with those of healthy relatives and neighbors. Officials so far have not revealed early findings, except to say they supported the investigation's new move.

Among the possibilities FDA has said it was exploring is whether tomatoes and other produce are sharing a common packing or shipping site where both might become contaminated, or whether multiple foods might be tainted while being grown on adjoining farms or with common water sources.

Officials have said some patients have told the Centers for Disease Control and Prevention they ate raw tomatoes in fresh salsa and guacamole.

CDC spokesman Glen Nowak said Saturday that the agency's scientists are working around the clock to try to pinpoint the source of the outbreak but are not ready to single out anything. Salsa ingredients, including peppers, are among the items being tested, Nowak said. "We don't rank the items we're looking at."



Scientists: Watermelon yields Viagra-like effects


LUBBOCK, Texas - A slice of cool, fresh watermelon is a juicy way to top off a Fourth of July cookout and one that researchers say has effects similar to Viagra — but don't necessarily expect it to keep the fireworks going all night long.

Watermelons contain an ingredient called citrulline that can trigger production of a compound that helps relax the body's blood vessels, similar to what happens when a man takes Viagra, said scientists in Texas, one of the nation's top producers of the seedless variety.

Found in the flesh and rind of watermelons, citrulline reacts with the body's enzymes when consumed in large quantities and is changed into arginine, an amino acid that benefits the heart and the circulatory and immune systems.

"Arginine boosts nitric oxide, which relaxes blood vessels, the same basic effect that Viagra has, to treat erectile dysfunction and maybe even prevent it," said Bhimu Patil, a researcher and director of Texas A&M's Fruit and Vegetable Improvement Center. "Watermelon may not be as organ-specific as Viagra, but it's a great way to relax blood vessels without any drug side effects."

Todd Wehner, who studies watermelon breeding at North Carolina State University, said anyone taking Viagra shouldn't expect the same result from watermelon.

"It sounds like it would be an effect that would be interesting but not a substitute for any medical treatment," Wehner said.

The nitric oxide can also help with angina, high blood pressure and other cardiovascular problems, according to the study, which was paid for by the U.S. Department of Agriculture.

More citrulline — about 60 percent — is found in watermelon rind than in the flesh, Patil said, but that can vary. But scientists may be able to find ways to boost the concentrations in the flesh, he said.

Citrulline is found in all colors of watermelon and is highest in the yellow-fleshed types, said Penelope Perkins-Veazie, a USDA researcher in Lane, Okla.

She said Patil's research is valid, but with a caveat: One would need to eat about six cups of watermelon to get enough citrulline to boost the body's arginine level.

"The problem you have when you eat a lot of watermelon is you tend to run to the bathroom more," Perkins-Veazie said.

Watermelon is a diuretic and was a homeopathic treatment for kidney patients before dialysis became widespread.

Another issue is the amount of sugar that much watermelon would spill into the bloodstream — a jolt that could cause cramping, Perkins-Veazie said.

Patil said he would like to do future studies on how to reduce the sugar content in watermelon.

The relationship between citrulline and arginine might also prove helpful to those who are obese or suffer from type-2 diabetes. The beneficial effects — among them the ability to relax blood vessels, much like Viagra does — are beginning to be revealed in research.

Citrulline is present in other curcubits, like cucumbers and cantaloupe, at very low levels, and in the milk protein casein. The highest concentrations of citrulline are found in walnut seedlings, Perkins-Veazie said.

"But they're bitter and most people don't want to eat them," she said.


Haywire brain chemical linked to sudden baby death

WASHINGTON - Scientists have new evidence that the brain chemical best known for regulating mood also plays a role in the mystifying killer of seemingly healthy babies — sudden infant death syndrome

Autopsied brain tissue from SIDS babies first raised suspicion that an imbalance in serotonin might be behind what once was called crib death.

But specialists couldn't figure out how that defect could kill. Now researchers in Italy have engineered mice born with serotonin that goes haywire — and found the brain abnormality is enough to spur sudden death, in ways that mesh with other clues from human babies.

Moreover, the work suggests it might one day be possible to test newborns for their risk of SIDS.

For now, even an animal experiment can offer a message for devastated families:

"It should provide them with some sense of comfort that there was nothing they could have done to prevent it," said Dr. Marian Willinger, a SIDS specialist at the National Institute of Child Health and Human Development, who wasn't part of the study. "It is a real disease."

The work was published in Friday's edition of the journal Science.

SIDS is the sudden death of an otherwise healthy infant — anywhere between ages 1 month and 1 year — that can't be attributed to any other cause. It kills more than 2,000 U.S. infants each year, and is the leading killer of babies after the newborn period.

Babies should always be placed to sleep on their backs, as the risk of SIDS increases greatly when babies sleep on their stomachs. And parents are urged not to allow anyone to smoke around their babies, or to let their babies get too warm while sleeping.

But beyond those risk factors, doctors have little advice.

In 2006, Dr. Hannah Kinney of Children's Hospital Boston compared brain tissue from 31 SIDS babies and 10 infants who died of other causes. The SIDS babies had abnormalities in their brain stem that led to imbalances in serotonin, a neurotransmitter or chemical that helps brain cells communicate.

Low serotonin famously plays a role in depression. Less known to laymen is that it also helps regulate some of the body's most basic functions — breathing, heart rate, body temperature, arousal from sleep.

Dr. Cornelius Gross and colleagues at the European Molecular Biology Laboratory in Italy were studying how the serotonin system turns itself on and off when they stumbled onto the SIDS connection.

They genetically engineered mice to have an overactive serotonin-regulating receptor, which in turn reduced the amount of serotonin in the brains of otherwise normal baby mice.

More than half of the mice abruptly died before they were 3 months old. More intriguing, they had erratic episodes where their heart rate would drop and, five to 10 minutes later, so would their body temperature, Gross reported. Sometimes they died in the midst of what Gross calls those crises, other times afterward.

The exact cellular defects in the mice and the human babies studied so far aren't identical, researchers caution.

But heart and temperature problems are consistent with what little human data is available, Willinger noted.

Here's another key: Gross could switch on and off the genetic defect that controlled serotonin levels in the mice. By doing so, he showed that older baby animals were less likely to die from haywire serotonin than younger ones.

"This is a very exciting part of the research," says Willinger — because doctors have long suspected that if at-risk babies just get through a developmental period, they'll be OK. That's impossible to test in humans, however

Study: Orangutan populations declining sharply


BANGKOK, Thailand - Orangutan numbers have declined sharply on the only two islands where they still live in the wild and they could become the first great ape species to go extinct if urgent action isn't taken, a new study says.

The declines in Indonesia and Malaysia since 2004 are mostly because of illegal logging and the expansion of palm oil plantations, Serge Wich, a scientist at the Great Ape Trust in Iowa, said on Saturday.

The survey found the orangutan population on Indonesia's Sumatra island dropped almost 14 percent since 2004, Wich said. It also concluded that the populations on Borneo island, which is shared by Malaysia, Brunei and Indonesia, have fallen by 10 percent. Researchers only surveyed areas of Borneo that are in Indonesia and Malaysia.

In their study, Wich and his 15 colleagues said the declines in Borneo were occurring at an "alarming rate" but that they were most concerned about Sumatra, where the numbers show the population is in "rapid decline."

"Unless extraordinary efforts are made soon, it could become the first great ape species to go extinct," researchers wrote.

The number of orangutans on Sumatra has fallen from 7,500 to 6,600 while the number on Borneo has fallen from 54,000 to around 49,600, according to the survey on the endangered apes, which appears in this month's science journal Oryx.

"It's disappointing that there are still declines even though there have been quite a lot of conservation efforts over the past 30 years," Wich said.

Indonesia and Malaysia, the world's top two palm oil producers, have aggressively pushed to expand plantations amid a rising demand for biofuels which are considered cleaner burning and cheaper than petrol.

Wich and his colleagues said there was room for "cautious optimism" that the orangutan could be saved, noting recent initiatives by Indonesian leaders.

Indonesian President Susilo Bambang Yudhoyono announced a major initiative to save the nation's orangutans at a U.N. climate conference last year, and the Aceh governor declared a moratorium on logging.

Coupled with that are expectations that Indonesia will protect millions of acres of forest as part of any U.N. climate pact that will go into effect in 2012. The deal is expected to include measures that will reward tropical countries like Indonesia that halt deforestation.

"There are promising signs that there is a lot of political will, especially in Aceh, to protect the forest," Wich said, adding however that much more needs to be done.

Michelle Desilets, founding director of Borneo Orangutan Survival Foundation UK, praised the study for offering the first comprehensive look at the species population.

"What matters is that the rate of decline is increasing, and unless something is done, the wild orangutan is on a quick spiral towards extinction, whether in two years, five years or 10 years," Desilets said in an e-mail.

In their paper, the researchers recommended that law enforcement be boosted to help reduce the hunting of orangutans for food and trade. Environmental awareness at the local level must also be increased.

"It is essential that funding for environmental services reaches the local level and that there is strong law enforcement," the study says. "Developing a mechanism to ensure these occur is the challenge for the conservation of the orangutans."

The study is the latest in a long line of research that has predicted the orangutans demise.

In May, the Center for Orangutan Protection said just 20,000 of the endangered primates remain in the tropical jungle of Central Kalimantan on Borneo island, down from 31,300 in 2004. Based on that estimate, it concluded orangutans there could be extinct by 2011

Microsoft, Yahoo mull media partner options: sources


SAN FRANCISCO/NEW YORK (Reuters) - Microsoft Corp and Yahoo Inc have been holding separate talks with other potential media partners after their negotiations with each other broke down, sources familiar with the companies' thinking said on Wednesday.
Microsoft -- rebuffed this year in efforts to buy all of Yahoo and then just its search business -- is talking about alternative deals with Time Warner Inc, which owns AOL, and News Corp, parent of MySpace, a source close to Microsoft said, but any negotiations remain in preliminary stages.

Meanwhile, talks have continued for months between Yahoo and Time Warner over a potential merger of AOL with Yahoo to create a more formidable advertising and media player, but they are no closer to a deal, a source close to the matter said.

Shares of Yahoo jumped as much as 9 percent on Wednesday after the Wall Street Journal reported that Microsoft, positioning for a new run for Yahoo's search business, had in recent days approached media companies to join together on a deal that would effectively lead to Yahoo's breakup.

However, a Reuters source and a CNBC report, citing unnamed sources, later said there were no new talks or negotiations.

The Journal also said Microsoft met with activist investor Carl Icahn in recent days to encourage him to press his proxy battle for control of Yahoo's board, the first sign Microsoft welcomed his month-old campaign. This development also was attributed to unnamed sources familiar with the talks.

Icahn was not available to comment on the report.

Microsoft, Yahoo, Time Warner and News Corp all declined comment.

REVIVING HOPE

Wall Street analysts said the latest news revived flagging hopes among some investors that Microsoft was still interested in doing a deal with Yahoo. "The hopes that Microsoft would come back were getting crushed over the last 10 trading days," Collins Stewart analyst Sandeep Aggarwal said.

Yahoo stock ended the day up 3.4 percent at $20.88. The stock had traded as low as $19.58 on Tuesday, near its level in late January before Microsoft made its unsolicited takeover bid for Yahoo, sending the stock above $30 by mid-February.

Microsoft shares fell 3.7 percent to $25.88 on Wednesday. In the prior day's trading, Microsoft fell to two-year lows of $23.19, intraday, before recovering.

Analyst Youssef Squali of Jefferies & Co said the sharp Yahoo stock reaction was most likely a defensive move by short-sellers seeking to cover bets a Microsoft deal was off.

"Even the rumor that Microsoft is getting interested again is enough to have people to want to cover their bets against Yahoo stock," Squali said, adding that many investors have shorted Yahoo from the high $20s all the way down below $20.

Adding to the volatility were options investors who placed fresh bets Yahoo would be trading up to $27.50 by October, said analyst Rebecca Engmann Darst of Interactive Brokers Group.

THE WAITING GAME

Several financial analysts said a key detail in the Journal report was that Microsoft and Yahoo executives had sought to revisit the merger on May 17 -- two weeks after Microsoft walked away -- and that two Yahoo board members in the meeting had said they would settle for a merger worth $33-$34 a share.

On May 3, Yahoo rejected a $33-a-share Microsoft offer worth $47.5 billion, and earlier this week questioned whether the software maker was ever serious about a full-scale merger.

The source familiar with Microsoft's thinking confirmed that Yahoo had belatedly sought a deal in mid-May worth $33 to $34, but that Microsoft was no longer interested at that point.

The source said Microsoft executives considered the early May deadline as vital to winning regulatory approval before the end of the year -- when a new presidential administration arrives and months more delays would likely occur.

Microsoft also become convinced that Yahoo executives were passively resisting the deal and unwilling to seriously negotiate. Meanwhile, the economy has taken a toll on the online ad market, and with it, the value of buying Yahoo.

"Microsoft is going to let Icahn do the dirty work and hand Yahoo over to them," Jefferies & Co's Squali said, adding that it was in Microsoft's interest to hang back and let Yahoo shares settle lower as investors quit betting on a takeover premium.

In the long run, however, Microsoft needs Yahoo more than Yahoo needs Microsoft, he argued.

"Microsoft has a gaping hole in its strategy and it's called the Internet and it's only getting worse because Google is encroaching on Microsoft's business," Squali said.

Separately, the U.S. Justice Department is pursuing a formal antitrust investigation into a deal reached last month between Yahoo and Microsoft-archrival Google Inc to team up on Web search advertising.

Google, with more than 60 percent of the Web search market, and Yahoo, with 16.6 percent, agreed to a deal for Google to run search ads on Yahoo's site in a partnership that could mean $250 million to $450 million in new cash flow for Yahoo.

Google said it was confident the deal would enhance overall industry competition, but declined to discuss the probe.


Chipmaker Connects A Wireless World And Makes It Run Faster

Laptops long ago stopped needing wires to be wired.

Now televisions, digital cameras and game consoles commonly link to the world without those physical ties.

Atheros Communications (NasdaqGS:ATHR - News) is helping cut the tethers.

The Santa Clara, Calif., semiconductor company develops chips for laptops, routers and other electronics that seamlessly link them to the world.

Intel (NasdaqGS:INTC - News) still dominates the market for wireless chips in laptops and routers. Analysts say it has about 70% of the space, with companies such as Atheros and Broadcom (NasdaqGS:BRCM - News) splitting the rest.

But analysts say Atheros is chipping away there and gaining market share. And as wireless Internet connections proliferate in cell phones and game systems, Atheros chips are finding new markets.

An Atheros chip on a digital camera memory card beams the photos to computers or printers without cables.

Its chips are inside Netflix's (NasdaqGS:NFLX - News) new set-top box, which lets viewers stream movies from the Internet to their TVs.

"The game in this segment is all about bringing in innovation and bringing down the cost curve. Atheros has been good at doing that," said Adam Benjamin, a semiconductor analyst with Jefferies & Co.

Faster Connection

The semiconductor industry is transitioning from the 802.11g network standard for wireless local area networks to the next-generation 802.11n.

Those 11n chips promise huge growth for the industry, since they can potentially transmit and receive more data, faster -- critical when beaming high-definition TV and other data-rich files.

And 11g chips are still selling briskly.

Atheros has reported 11 straight quarters of double-digit year-over-year sales growth.

It had record 11g sales in the first quarter.

Most of its chips go to electronics manufacturers in Asia.

Taiwanese hardware manufacturer Hon Hai Precision Industry is its largest customer, accounting for a quarter of last year's sales.

Atheros has deals with major PC makers such as Acer, Hewlett-Packard (NYSE:HPQ - News), Lenovo and Toshiba. This month, Atheros said Advanced Micro Devices (NYSE:AMD - News) would bundle its 11n chip with some of its notebook processors.

Atheros chips were dropped recently by a major PC maker. The company didn't name it, but most analysts think it was Apple (NasdaqGS:AAPL - News).

In part because of that, as well as seasonal fluctuations, Atheros sales were flat between the first and fourth quarters.

But year-over-year sales rose 20% in the first quarter to $114.5 million. Earnings per share climbed 22% to 28 cents.

Atheros' 11g chips gained market share in wireless local area network routers, used to set up Internet hot spots and home networks.

Those 11g sales should taper off in coming years.

But sales should pick up on the higher-priced 11n chips as laptops, wireless routers and cell phones increasingly use the faster next-generation standard.

Those PC and Wi-Fi networks remain a big part of Atheros' business.

The company is also reaching into other communications technology platforms.

It's gaining bigger physical footprints within traditional laptops and wireless routers.

And it's getting into cell phones and portable game players.

"If you think that Atheros is just focused on wireless LAN, frankly we shouldn't be all that interesting to invest in," Atheros Chief Financial Officer Jack Lazar said during an investors conference. "What we're really trying to do is a variety of communications platforms that address the markets that we've already started to open up or the customers that we've already started to open up."

In 2006, Atheros bought Attansic Technology, a Taiwanese developer of ethernet integrated circuits. Last December, it bought u-Nav Microelectronics, a private developer of Global Positioning System chips and software for cell phones and other personal handsets.

Atheros internally developed its own Bluetooth products, which it started selling last year.

The company expects growth in Bluetooth, ethernet and the Global Positioning System. The mobile wireless LAN business is one of its fastest growers.

High-volume consumer items lead the way. Its chips are reaching cell phones, digital music players and other handheld electronics, as cost per chip and power consumption fall. Atheros claims more than 30 design wins for handsets.

One win is likely Nintendo's handheld DS game system, analysts say, though the company won't confirm it.

Atheros says wireless LAN chips in the unnamed game system should drive revenue in the second half of this year.

Analysts at Piper Jaffray think the deal could mean 4 million chips per quarter, at $3 to $4 each.

But Abdul Saleh, an analyst at Zacks Investment Research, thinks those games and other wireless LAN chips might not deliver much until the December quarter.

"It's probably an end-of-the-year story, rather than a second-half story," Saleh said.

So barring some big news when second-quarter results are announced next month, Saleh thinks much of those wins are already priced into the stock.

Competition And Risks

Risks exist. Purchases of wireless routers and PCs could slow. There's the chance of slower-than-expected adoption of wireless technology in handheld electronics.

Competition remains a key challenge. Atheros faces off against larger players, such as Intel , Broadcom , Texas Instruments (NYSE:TXN - News) and Marvell Technology (NasdaqGS:MRVL - News). Smaller firms include Conexant Systems (NasdaqGS:CNXTD - News).

Other competitors might arise as the handset market and the overall 11n market grow. That competition is already pushing prices lower for Atheros' legacy 11g chips, which are still more than half its sales.

Most analysts think sales and revenue should hold up. Those surveyed by Thomson Reuters project 20% top- and bottom-line boosts in the second quarter.

For the year, the consensus is for earnings per share to rise 17% in 2008 to $1.31. For 2009, analysts expect a 19% increase to $1.56.


iPhone 3G queue forms in Manhattan

The line for the Apple iPhone 3G began to form Friday--an entire week before the device goes on sale.

Frankly, one shouldn't encourage such behavior by actually covering it. But if I were in Manhattan--instead of Austin, Texas--I, too, would have interviewed them in person by now.

The queue outside of Apple's Fifth Avenue store, covered first by GearDiary and then Engadget, apparently hasn't been formed by iPhone co-dependents, though.

It is instead made up of a group of people who may want to 1) set a world's record for standing in line to buy a product and 2) have a social-agricultural-political message they want the world to hear. However, it was difficult from the video interview on Engadget to determine what the group actually stands for.

On Saturday, the Apple 2.0 blog seemed to get further with the group's agenda. The group, which started off with about 10 on Friday and was slimmed down to 5 by Saturday morning after a night of rainfall, apparently supports organic farming and sustainability for the planet. According to Apple 2.0, they may be interested in turning the White House Lawn into an organic garden and they may be planning to buy iPhones for the presidential nominees.

The seemingly ad hoc group is certainly savvy in deciding to use the iPhone 3G to garner some publicity. However, to be perfectly honestly, most mainstream journalists feel more comfortable interviewing gadget nuts rather than alternative souls hoping to use the media to change the world.